62023CC0314
OPINION OF ADVOCATE GENERAL
SZPUNAR
delivered on 6 June 2024 (
1
)
Case C‑314/23
Sindicato de Tripulantes Auxiliares de Vuelo de Líneas Aéreas (STAVLA),
Ministerio Fiscal
v
Air Nostrum, Líneas Aéreas del Mediterráneo SA,
Federación de Servicios de Comisiones Obreras (CCOO),
Unión General de Trabajadores (UGT),
Unión Sindical Obrera (USO),
Comité de empresa de Air Nostrum Líneas Aéreas del Mediterráneo SA,
Dirección General de Trabajo,
Instituto de las Mujeres,
Interested parties:
Sindicato Español de Pilotos de Líneas Aéreas (SEPLA),
Sindicato Unión Profesional de Pilotos de Aerolíneas (UPPA)
(Request for a preliminary ruling from the Audiencia Nacional (National High Court, Spain))
(Reference for a preliminary ruling – Implementation of the principle of equal opportunities and equal treatment of men and women in matters of employment and occupation – Directive 2006/54/EC – Article 14 – Prohibition of any indirect discrimination on grounds of sex – Collective agreements establishing different amounts of daily subsistence allowances to be granted to pilots and cabin crew as a meal allowance while travelling)
I. Introduction
1.
Can the fact that an airline’s cabin crew members receive a lower daily subsistence allowance to cover meal costs incurred during work-related travel than the allowance received by pilots be objectively justified under Directive 2006/54/EC (
2
) where that difference arises from the application of two collective agreements? That question is central to the present case.
2.
The request for a preliminary ruling from the Audiencia Nacional (National High Court, Spain) concerns the interpretation of Article 14(1)(c) of Directive 2006/54.
3.
The request has been made in proceedings between a trade union representing cabin crew and an airline, concerning an action for partial annulment of the collective agreement applicable to the airline’s cabin crew.
4.
The present case presents the Court of Justice with a further opportunity to reconsider issues relating to the prohibition of any discrimination based on sex in matters of employment and occupation and, in particular, the question of objective justification of a measure which introduces unequal treatment in working conditions where that inequality arises from the application of two separate collective agreements negotiated by the employer with different trade unions.
II. Legal framework
A. European Union law
5.
Article 2 of Directive 2006/54, entitled ‘Definitions’, states in paragraph 1:
‘For the purposes of this Directive, the following definitions shall apply:
…
(b)
“indirect discrimination”: where an apparently neutral provision, criterion or practice would put persons of one sex at a particular disadvantage compared with persons of the other sex, unless that provision, criterion or practice is objectively justified by a legitimate aim, and the means of achieving that aim are appropriate and necessary;
…’
6.
Article 14 of that directive, entitled ‘Prohibition of discrimination’, provides in paragraph 1:
‘There shall be no direct or indirect discrimination on grounds of sex in the public or private sectors, including public bodies, in relation to:
…
(c)
employment and working conditions, including dismissals, as well as pay as provided for in Article 141 of the Treaty;
…’
B. Spanish law
7.
The Real Decreto Legislativo 2/2015 por el que se aprueba el texto refundido de la Ley del Estatuto de los Trabajadores (Royal Legislative Decree 2/2015 approving the consolidated text of the Law on the Workers’ Statute) of 23 October 2015 (
3
) (‘the Law on the Workers’ Statute’), provides in Article 3, entitled ‘Sources of the employment relationship’:
‘1.   Rights and obligations concerning the employment relationship are governed by:
(a)
national laws and regulations;
(b)
collective agreements;
…’
8.
Article 4(2)(c) of that law provides:
‘Workers have the right, in their employment:
…
(c)
not to be discriminated against directly or indirectly, when seeking employment or once in employment, on the basis of sex …’
9.
Article 17(1) of that law reads as follows:
‘Any regulatory provisions, clauses of collective agreements, individual agreements and unilateral decisions of the employer which, in matters of employment, remuneration, working hours or other working conditions, give rise to situations of direct or indirect discrimination on grounds of sex shall be regarded as void and without effect …’
10.
Under Article 26(2) of the same law:
‘Sums received by a worker by way of reimbursement or allowances for expenses incurred as a consequence of his or her work, social security benefits and allowances and compensation for relocation, suspension or dismissal shall not be regarded as salary.’
11.
Under Article 87 of the Law on the Workers’ Statute:
‘1.   The works council, where appropriate staff delegates, or trade union branches if they together make up the majority of members of the council, shall be authorised to negotiate collective agreements at the level of the undertaking or lower on the workers’ behalf.
Negotiations shall be conducted by trade union branches where they so agree, provided that they make up the majority of the members of the works council or staff delegates.
…
In agreements aimed at a group of workers with a specific occupational profile, the trade union branches which have been designated by a majority of the individuals they represent by means of personal, free, direct and secret ballot, shall have the authority to negotiate.’
12.
The IV Convenio colectivo de Air Nostrum (personal de tierra y TCP’S) (
4
) (Fourth Air Nostrum Collective Agreement (Ground Staff and Cabin Crew)), registered and published by the Resolución de la Dirección General de Trabajo (Resolution of the Directorate-General of Labour, Spain) of 18 December 2018, (
5
) in the version applicable to the facts in the main proceedings (‘the Cabin Crew Agreement’), signed by company management and the trade unions, Unión general de trabajadores (General Workers’ Union (UGT)), Federación de Servicios de Comisiones Obreras (Workers’ Commissions Services Federation (CCOO)) and Unión Sindical Obrera (Workers’ Syndical Union (USO)), governs the terms and conditions of employment of cabin crew in Articles 59 to 93.
13.
Article 93 of the Cabin Crew Agreement, entitled ‘Daily subsistence allowances’, defines the term ‘daily subsistence allowance’ as ‘the amount which compensates the [cabin crew member] for expenses incurred during travel, which form an integral part of his or her employment’. Under that article, ‘it is expressly agreed that that system of daily subsistence allowances exempts the company from covering subsistence costs during travel’.
14.
The Convenio Colectivo de Air Nostrum (pilotos) (Air Nostrum Collective Agreement (Pilots)), registered and published by the Resolución de la Dirección General de Trabajo (Resolution of the Directorate-General of Labour) of 10 March 2020, (
6
) in the version applicable to the facts in the main proceedings (‘the Flight Crew Agreement’), signed by company management and branches of the trade unions, Sindicato Español de Pilotos de Líneas Aéreas (Spanish Airline Pilots’ Union (‘SEPLA’)) and Sindicato Unión Profesional de Pilotos de Aerolíneas (Professional Airline Pilots’ Union (‘UPPA’)), governs the employment relationships of pilots (‘flight crew’).
15.
Article 16(19) of the Flight Crew Agreement, entitled ‘Daily subsistence allowances’, provides that the ‘daily subsistence allowance is the amount received by the pilot to cover expenses incurred during travel on the company’s behalf or stays away from his or her base. It does not include accommodation or transport’. The article states that it is expressly agreed that that system of daily subsistence allowances exempts the company from covering the cost of meals of any kind.
III. The facts of the case in the main proceedings, the question referred for a preliminary ruling and the procedure before the Court
16.
Employment relationships between Air Nostrum, Líneas Aéreas del Mediterráneo SA (‘Air Nostrum’) and its cabin crew are governed by the Cabin Crew Agreement, and employment relationships between Air Nostrum and its flight crew are governed by the Flight Crew Agreement. Article 93 of the Cabin Crew Agreement and Article 16(19) of the Flight Crew Agreement govern daily subsistence allowances covering, in particular, expenses incurred by cabin crew and flight crew respectively when travelling in the course of their employment (‘daily subsistence allowances’).
17.
On 8 November 2022, the Sindicato de Tripulantes Auxiliares de Vuelo de Líneas Aéreas (Airline Flight Attendants’ Union, (‘STAVLA’)), a trade union representing cabin crew, brought an action before the referring court for the protection of fundamental rights through the procedure for challenging a collective agreement (procedimiento de impugnación de convenio colectivo), seeking, in particular, the annulment of Article 93 and Annex I to the Cabin Crew Agreement in so far as Article 93 sets the amount of daily subsistence allowances. According to the trade union, since, as the referring court states, women represent 94% of cabin crew and men 93.71% of flight crew, the fact that the amount of daily subsistence allowances provided for in the Cabin Crew Agreement is significantly lower than that provided for in the Flight Crew Agreement to deal with the same situation constitutes indirect discrimination based on sex in working conditions, prohibited by Article 14(1)(c) of Directive 2006/54.
18.
The referring court states that the sums paid by way of daily subsistence allowances are not regarded as pay, either from the standpoint of Spanish employment law, since they are expressly excluded from the concept of ‘salary’ in Article 26(2) of the Law on the Workers’ Statute, or from the point of view of EU law, pursuant to Article 157 TFEU and Article 2(1)(e) of Directive 2006/54. That court submits that, since those allowances do not remunerate specific work calculated per unit of time or per unit of work, the different value of the work performed by flight crew and cabin crew cannot constitute a circumstance justifying unequal treatment as regards the amount of those allowances. Such allowances, paid to cover expenses incurred during travel, such as daily meals away from the usual place of residence, therefore fall within the scope of working conditions.
19.
According to the referring court, the result is that within Air Nostrum, one group of workers, consisting mainly of women, receives an amount significantly lower in compensation for expenses incurred during travel, in particular for food, than another group of workers, consisting mainly of men, receives to cover the same expenses.
20.
The referring court considers that indirect discrimination on grounds of sex would exist if different daily subsistence allowances had been established in the same collective agreement. (
7
) However, it doubts whether such discrimination exists in the present case in so far as the difference in treatment owes to the fact that the company applies two different collective agreements negotiated with different trade union representatives. It must therefore be assumed that, in each negotiation process, each group of trade union representatives prioritised some claims over others vis-à-vis the airline.
21.
In addition, the referring court points out that, when Air Nostrum negotiated the Flight Crew Agreement, the Cabin Crew Agreement had already been signed and Air Nostrum was therefore aware of the amounts set for daily subsistence allowances for cabin crew.
22.
In those circumstances, the Audiencia Nacional (National High Court), by decision of 17 March 2023, received at the Court on 22 May 2023, stayed proceedings and referred the following question to the Court of Justice for a preliminary ruling:
‘Does the fact that [Air Nostrum] compensates a group such as cabin crew, where the majority of the individuals making up the group are women, for the expenses which they have to meet when travelling, other than those related to transport and accommodation, with an amount smaller than that received for the same expenses by another group of employees, such as pilots, in which the majority are men, constitute an instance of indirect discrimination on grounds of sex in relation to working conditions, contrary to European Union law and prohibited under Article 14(1)(c) of Directive 2006/54, where the reason for such different treatment lies in the fact that each group is subject to a different collective agreement, both negotiated by the same company but with different union representatives, pursuant to Article 87 of the [Law on the Workers’ Statute]?’
23.
Written observations were filed by the Ministerio Fiscal (Public Prosecutor’s Office, Spain), SEPLA, the Spanish, Danish and Swedish Governments and the European Commission.
24.
The file before the Court shows that STAVLA withdrew its action on 21 September 2023. While the other parties to the main proceedings did not oppose the withdrawal and the removal of the case from the register, the Public Prosecutor’s Office took the view that the action should be maintained. (
8
)
25.
By order of 26 October 2023, the referring court noted STAVLA’s withdrawal but maintained its request for a preliminary ruling, the Public Prosecutor’s Office being regarded as the applicant replacing STAVLA.
26.
The Public Prosecutor’s Office, Air Nostrum, UGT, SEPLA, the Spanish, Danish and Swedish Governments and the Commission were represented at the hearing on 19 March 2024.
IV. Assessment
27.
By its question referred for a preliminary ruling, the national court seeks, in essence, to ascertain whether Article 14(1)(c) of Directive 2006/54 must be interpreted as precluding a practice whereby an airline pays cabin crew, the majority of whom are women, a daily subsistence allowance to cover meal costs incurred during work-related travel of a lower amount than the allowance paid to flight crew, the majority of whom are men, for the same expenses, where that inequality of treatment arises from the application of two separate collective agreements negotiated by the employer and different trade unions.
28.
On that point, the parties to the main proceedings are divided as to whether there is discrimination on grounds of sex disadvantaging cabin crew. Air Nostrum and SEPLA, as well as the Danish and Swedish Governments, do not deny such discrimination but consider it justified by the social partners’ autonomy in negotiating and concluding collective agreements applying to the workers they represent. Thus, a collective agreement should be applied without regard to other collective agreements which the same employer may have concluded with the trade union representatives of other groups of employees.
29.
By contrast, UGT submits that there is indirect discrimination in so far as the difference in treatment at issue cannot be objectively justified on the basis of the right to collective bargaining. It argues that the fact that the difference in treatment arises from the application of two separate collective agreements negotiated by the employer with different trade unions has no bearing on the lack of justification under the provisions of Directive 2006/54. The Public Prosecutor’s Office submits that the Cabin Crew Agreement indirectly discriminates in respect of working conditions within the same company, which is unacceptable irrespective of the source of that discrimination, in so far as exercise of the right to collective bargaining cannot be regarded as an objective justification. The right to collective bargaining is established in EU law and must be exercised in accordance with that law. The Spanish Government and the Commission argue that it is for the referring court to determine whether the discrimination at issue is justified. That being so, for the purposes of the present case, the mere fact that that discrimination arises from two collective agreements is not sufficient, in their view, to justify the difference in treatment at issue in the light of the provisions of Directive 2006/54.
30.
Against that background, in order to be able to propose a helpful answer to the referring court, it must, first of all, be determined whether the daily subsistence allowances at issue in the main proceedings provided for by the Cabin Crew Agreement fall within the scope of Directive 2006/54 (Section B) and, secondly, whether the payment of those allowances is liable to result in discrimination on grounds of sex prohibited by that directive (Section C). Before embarking on that assessment, I consider it necessary to set out some brief introductory remarks on the primary and secondary law relating to the principles of equality, equal treatment and non-discrimination in connection with which the present dispute has arisen (Section A).
A. Preliminary remarks
31.
At the outset, I would observe that the European Union is founded on a set of values enshrined in Article 2 TEU. Those values, of which ‘respect for equality’ forms an integral part alongside human dignity, freedom, democracy, the rule of law and respect for human rights, ‘constitute the core of [the EU’s] identity’. (
9
) According to Article 2 TEU, those values are common to the Member States in a society in which, in particular, non-discrimination and equality between women and men prevail. The second subparagraph of Article 3(3) TEU provides that, when establishing an internal market, the EU is to combat discrimination and promote equality between women and men. Furthermore, Article 21(1) of the Charter of Fundamental Rights of the European Union (‘the Charter’) prohibits any discrimination on grounds of sex, that provision being a specific expression of the general principle of equal treatment recognised in Article 20 of the Charter. (
10
) Equality between men and women is also enshrined in Article 23 of the Charter.
32.
Concerning Directive 2006/54, recital 2 thereof states that ‘equality between men and women [is both] a “task” and an “aim” of [the European Union]’. That recital also recalls the status of such equality as a ‘fundamental principle of [EU] law’ under Articles 2 and 3(2) TFEU. (
11
) Moreover, Directive 2006/54 was adopted on the basis of Article 141(3) of the EC Treaty (now Article 157(3) TFEU). According to recital 4, Directive 2006/54 provides ‘a specific legal basis for the adoption of … measures to ensure the application of the principle of equal opportunities and equal treatment in matters of employment and occupation’. Thus, Directive 2006/54 aims, pursuant to Article 1 thereof, to ensure the implementation of that principle in employment and occupation. In accordance with that objective, Article 14(1)(c) of Directive 2006/54 prohibits any direct or indirect discrimination on grounds of sex in relation to employment and working conditions.
33.
That, then, is the general context of the question referred by the national court for a preliminary ruling.
B. The existence of indirect discrimination on grounds of sex prohibited by Directive 2006/54
34.
The starting point for my assessment is the question whether the payment of the daily subsistence allowances at issue in the main proceedings falls within the scope of Directive 2006/54.
35.
The referring court states that those daily subsistence allowances, in so far as they constitute compensation paid by the airline to its employees to cover costs incurred during work-related travel, such as, first and foremost, daily meals away from their usual place of residence, fall within the scope of ‘working conditions’. (
12
)
36.
Consequently, there can be little doubt that the daily subsistence allowances at issue in the main proceedings fall within the material scope of Directive 2006/54 in so far as point (b) of the second paragraph of Article 1 thereof seeks to implement the principle of equal treatment as regards ‘working conditions’. I therefore consider that directive applicable to the present case.
37.
As regards the assessment of whether there is indirect discrimination on grounds of sex, I would point out at the outset that it is for the referring court to ascertain, having regard to the factual circumstances of the case, whether the payment of the daily subsistence allowances at issue in the main proceedings constitutes indirect discrimination on grounds of sex prohibited by Directive 2006/54.
38.
Article 2(1)(b) of Directive 2006/54 defines ‘indirect discrimination’ as a situation where an apparently neutral provision, criterion or practice would put persons of one sex at a particular disadvantage compared with persons of the other sex, unless that provision, criterion or practice is objectively justified by a legitimate aim, and the means of achieving that aim are appropriate and necessary. (
13
) It follows from that definition that indirect discrimination for the purposes of Directive 2006/54 occurs when the three conditions set out therein are satisfied.
39.
Consequently, in order to assess whether there is indirect discrimination prohibited by Directive 2006/54, it is appropriate to follow the normative structure of Article 2(1)(b) thereof and carry out a three-stage analysis. To that end, I shall first address the question of whether the measure in question is apparently neutral (Section 1). (
14
) I shall then consider whether the measure places persons of one sex at a particular disadvantage compared with persons of the other sex (Section 2). Lastly, I shall assess whether such a particular disadvantage is justified by objective factors unrelated to any discrimination on grounds of sex (Section 3).
1.
Is the practice at issue in the main proceedings apparently neutral?
40.
At the outset, I would recall that, unlike direct discrimination, indirect discrimination is characterised not by the appearance of a national measure (or its author’s intent), but by its possible adverse effect. In general terms, the question is therefore whether a given measure or practice, neutral only in appearance, is likely to have a ‘harmful or undesirable effect’ on persons of one sex compared with those of the other sex. (
15
) In other words, such a measure or practice is not directly based on a prohibited ground of discrimination, since the determining factor for assessing the existence of indirect discrimination is the disparity between the two groups. (
16
)
41.
In the present case, it is clear from the order for reference that the payment of the daily subsistence allowances at issue in the main proceedings does not constitute direct discrimination based on grounds of sex for the purposes of Article 2(1)(a) of Directive 2006/54, since the provisions of the collective agreements which provide for those allowances (or the amount of the allowances giving rise to a difference in treatment) are formally neutral. Those allowances are paid by the airline to the male and female workers concerned without distinction. (
17
)
42.
Thus, the referring court is inclined to take the view that the payment of the daily subsistence allowances at issue in the main proceedings gives rise to indirect discrimination prohibited by Article 14(1)(c) of Directive 2006/54. In that regard, that court notes that such an apparently neutral practice establishes a difference in treatment between cabin crew and flight crew, and consequently between women and men.
2.
Does the practice at issue in the main proceedings place persons of one sex at a particular disadvantage compared with persons of the other sex?
43.
The present case is distinctive in that the difference in treatment resulting from the employer’s payment of daily subsistence allowances arises from the application of the respective provisions of the Cabin Crew and Flight Crew Agreements. According to the referring court, the amount paid to cover meal expenses during work-related travel to cabin crew, who are mainly women, is lower than that paid to flight crew, who are mainly men, for the same expenses. In that court’s view, such an apparently neutral practice giving rise to a difference in treatment as a result of the application of those agreements may place cabin crew at a disadvantage.
44.
Before assessing whether the practice at issue in the main proceedings is liable to give rise to such a comparative disadvantage for the purposes of Article 2(1)(b) of Directive 2006/54, I consider it useful to make the following observations.
(a)
General considerations regarding the comparison
45.
With regard to the principle of equal treatment, the Court has stated that discrimination ‘involves the application of different rules to comparable situations or the application of the same rule to different situations’. (
18
) As academic commentators point out, the definitions based on the Court’s case-law concerning, in particular, direct and indirect discrimination still remain essential in areas where the EU legislature has not defined those concepts. Against that background, the concept of ‘indirect discrimination’ for the purposes of EU social law relates first and foremost to different treatment of comparable situations. (
19
)
46.
As regards the areas in which the EU legislature has codified the concepts of the various forms of discrimination developed by the Court in its case-law, (
20
) it is for the national court, which alone is competent to assess the facts of the case before it and to interpret the applicable national legislation, to determine, in the context of those concepts and that case-law, whether discrimination of the alleged type or possibly another is present in this case. (
21
)
47.
As I have already explained, direct or indirect discrimination for the purposes of Directive 2006/54 is established only where the conditions laid down by the respective provisions are met. In particular, in assessing the condition of the ‘comparability of situations’ in the context of the concept of direct discrimination (Article 2(1)(a)) or that of the ‘particular disadvantage faced by persons of one sex compared with persons of the other sex’ in the context of indirect discrimination (Article 2(1)(b)), it seems to me important to bear in mind that the comparison to be performed will vary according to the type of discrimination in question and, consequently, according to the normative structure of the provision in which that condition appears. (
22
)
48.
In that connection, the definition of ‘direct discrimination’ in Article 2(1)(a) of Directive 2006/54 explicitly mentions the requirement that situations be comparable (‘in a comparable situation’). (
23
) Accordingly, it is clear from the Court’s settled case-law that the existence of direct discrimination presupposes that the situations under consideration are comparable. (
24
)
49.
Conversely, the definition of ‘indirect discrimination’ provided in Article 2(1)(b) of Directive 2006/54 does not mention any requirement for the situations to be comparable. Indeed, the words ‘persons of one sex … compared with persons of the other sex’ in that second provision merely refer to the particular disadvantage to which an apparently neutral provision, criterion or practice puts one group of persons as compared with another group of persons rather than to any comparability of situations. (
25
) Therefore, although a comparison must be performed in both cases, it is not exactly the same for direct discrimination as indirect discrimination, as defined in Article 2(1)(a) and (b) of that directive. (
26
)
50.
With regard to Article 2(1)(b) of Directive 2006/54, academic authors note that ‘a finding of indirect discrimination does not require the comparability of the respective situations of those benefitting from favourable treatment and those suffering unfavourable treatment’. (
27
) In other words, it does not follow from Article 2(1)(b) of the Directive that the comparison must be made only with workers in an identical or similar situation (for example, only part-time workers). (
28
) Rather, the groups compared should include all workers who are affected
by the measure, that is, the contested
provision, criterion or practice (for example, part-time workers with full-time workers). (
29
) Indeed, in so far as differences in the situation of the particularly disadvantaged group are considered unimportant in the light of the comparison criterion applied (making it possible to establish the existence of the contested difference), the question only arises as to whether, although there is a comparative disadvantage to the detriment of one of the two groups, the distinction between these groups is appropriate and necessary to achieve a legitimate aim.
51.
Thus, under Article 2(1)(b) of Directive 2006/54, in order to establish indirect discrimination, it is necessary to identify a particular disadvantage, a comparison criterion – for example a particular number of groups compared, namely groups of workers affected by the measure – and a lack of objective justification. Academic authors point out that, when interpreting the directives on equal treatment, the question of comparison has often been examined by the Court in its case-law on indirect discrimination in the framework of objective justification. (
30
)
52.
That being so, and bearing in mind the points I have just made, I shall now examine Air Nostrum and SEPLA’s argument that it is inappropriate to identify flight crew as a comparator in order to perform a comparison to establish whether the disadvantaged group, namely cabin crew, have suffered indirect discrimination. Indeed, since the identification of the comparator for the comparison precedes the assessment of the objective justification from a conceptual point of view, for the sake of clarity I shall address that point before specifically examining the particular disadvantage that the practice in question entails for the cabin crew compared to flight crew. (
31
)
(b)
The supposedly inappropriate identification of flight crew as a comparator for the purposes of a comparison in the context of alleged indirect discrimination
53.
According to the order for reference, in the main proceedings Air Nostrum and SEPLA argued in their written and oral submissions that the situation of cabin crew ‘is not comparable’ to that of flight crew in so far as the daily subsistence allowances at issue should be regarded as ‘pay’ and the principle of equal pay applies only where both groups of workers perform work which is identical or of the same value, which is not the case for cabin and flight crew.
54.
I disagree. That argument confuses, first, the ‘comparability of situations’ required to assess direct discrimination with the identification of a comparator that applies in a comparison to determine the existence of a particular disadvantage giving rise to indirect discrimination under Directive 2006/54, (
32
) and, secondly, the question of unequal treatment in respect of pay with that of unequal treatment in respect of working conditions under that directive. In other words, those parties are in effect seeking to redefine the purpose of the comparison, which concerns daily subsistence allowances falling within the scope of working conditions, as a question of equal pay. (
33
)
55.
As regards, first, inequality of treatment as regards ‘working conditions’, the referring court explains that the sums paid by way of daily subsistence allowances cannot be regarded as ‘pay’ since they are expressly excluded from the concept of ‘salary’ in Article 26(2) of the Law on the Workers’ Statute. According to that court, the allowances do not vary according to the value of the work of the employees concerned but, as I have already explained, (
34
) fall within the scope of ‘working conditions’ for the purposes of Directive 2006/54, in so far as they are paid solely to cover expenses incurred during work-related travel, such as, first and foremost, daily meals away from the habitual place of residence.
56.
The Spanish Government, the Public Prosecutor’s Office and the Commission agree with that view in their written and oral observations and submit that the daily subsistence allowances in question do not constitute pay. In their view, those allowances do not remunerate specific work calculated in units of time or work, but fall under the concept of ‘salary supplement’ and, accordingly, relate to the working conditions of cabin and flight crew during their work-related travel. UGT defended the same point of view at the hearing. As the Commission observes, those allowances do not depend on a pilot or flight attendant’s experience. (
35
) It therefore appears that, on a flight operated by the airline in question, a captain receives the same daily subsistence allowance as a co-pilot and a purser the same as a flight attendant, even though they are highly unlikely to be paid the same salary.
57.
As regards, secondly, the identification of the comparison criterion, namely the comparator to be used in a comparison for the purposes of Directive 2006/54, I have already explained that, in the context of direct discrimination, similar situations must be compared, whereas, in the context of indirect discrimination, a comparative disadvantage experienced by one of the two groups of people affected by the measure must be identified. (
36
) Indirect discrimination on grounds of sex essentially concerns the impact of a measure on different groups of people. It is therefore a matter of determining whether that measure is liable to advantage or disadvantage the group belonging to one sex in comparison with the other and thereby establishing a comparative disadvantage for one of them. (
37
)
58.
In the present case, in order to establish the existence of different treatment in the case in the main proceedings, the referring court selects payment of daily subsistence allowances by the employer, thereby designating as the relevant comparison criterion (the tertium comparationis) groups of people benefiting from the payment of the allowances giving rise to the difference to be justified. That court thereby identifies the disadvantaged group of workers (cabin crew) who, in a situation of work-related travel, are treated differently from another group (flight crew) in terms of working conditions within the meaning of Directive 2006/54. (
38
)
59.
It follows, in my view, that the amount of the daily subsistence allowances at issue in the main proceedings selected by the referring court is a valid point of comparison which reveals the particular disadvantage experienced by cabin crew compared with flight crew in a situation of work-related travel. I further note that the comparative disadvantage must be identified not in the abstract but only in relation to the provision, criterion or practice concerned giving rise to that particular disadvantage. (
39
) In other words, the general aim of the measure in question must be taken into account.
60.
In the present case, in order to determine the comparative disadvantage faced by cabin crew compared with flight crew, the purpose of the daily subsistence allowances at issue in the main proceedings must be ascertained. On that point, the order for reference makes it clear that the purpose is the same for both groups of workers concerned, namely compensation by the employer for the meal costs which those workers incur during their work-related travel, separately from the costs of transport and accommodation. That was confirmed at the hearing by the Public Prosecutor’s Office and the Commission.
61.
Therefore, from the point of view of its purpose, the payment of daily subsistence allowances makes it possible to identify a particular disadvantage suffered by a predominantly female group of persons (cabin crew) in relation to another, predominantly male group of persons (flight crew), as a valid comparison criterion.
(c)
The existence of a particular disadvantage for persons of one sex compared with persons of the other sex
62.
Under the Court’s settled case-law, the existence of a particular disadvantage might be established, in particular, if it were proved that an apparently neutral provision, criterion or practice adversely affects a significantly greater proportion of persons of one sex than persons of the other sex. It is for the national court to assess whether that is so in the main proceedings. (
40
)
63.
On that point, the Court has long recognised the usefulness of statistics in ascertaining the existence or otherwise of indirect discrimination. (
41
) Against that background, statistical data play a key role here in determining whether persons of one sex are in fact disadvantaged as compared with persons of the other sex. It is nevertheless for the national court to assess the reliability of those data and whether they can be taken into consideration. (
42
) If that court finds that the payment of daily subsistence allowances at issue in the main proceedings affects a higher percentage of women than men, that payment would constitute unequal treatment contrary to Article 14(1)(c) of Directive 2006/54.
64.
In order to assess those data, I would note that the Court of Justice has held that it is for the national court, first, to take into account all those workers subject to the national rule in which the difference in treatment has its origin, (
43
) and, secondly, to compare the respective proportions of workers who are and are not affected by the alleged difference in treatment among the men in the workforce who come within the scope of that rule with the same proportions of women in the workforce coming within its scope. (
44
)
65.
In the present case, as I have stated, according to the statistics available to the referring court, women represent 94% of cabin crew (6% being men) and men 93.71% of flight crew (6.29% being women). The amount of daily subsistence allowances provided for in the Cabin Crew Agreement is significantly lower than that provided for in the Flight Crew Agreement in the same situation of work-related travel. (
45
) Those data therefore show that the proportion of female workers affected by the difference in treatment arising from the payment of the daily subsistence allowances at issue in the main proceedings is significantly greater than the proportion of male workers.
66.
I am therefore of the view that if the referring court, on the basis of the statistics examined above and other relevant information as the case may be, concluded that the practice at issue in the main proceedings places cabin crew composed mostly of women at a particular disadvantage, then that practice should be found to be contrary to Article 14(1)(c) of Directive 2006/54, unless it were justified by objective factors unrelated to any discrimination on grounds of sex. (
46
)
3.
To what extent is the allegedly discriminatory practice objectively justified?
67.
At the outset, I would recall that Directive 2006/54 draws a distinction between direct and indirect discrimination based on sex, in that the former cannot be justified by a legitimate aim. (
47
) By contrast, under Article 2(1)(b) of that directive, provisions, criteria or practices liable to constitute indirect discrimination may avoid classification as ‘discrimination’ provided that they are ‘objectively justified by a legitimate aim, and that the means of achieving that aim are appropriate and necessary’.
(a)
The legitimacy of the aim relied on to justify the practice at issue in the main proceedings
68.
It follows from the Court’s case-law that, while it is ultimately for the national court, which has sole jurisdiction to assess the facts and interpret the national legislation, to determine whether and to what extent the practice in question is justified by objective factors unrelated to any discrimination based on sex, the Court of Justice, which is called on to provide answers of use to the national court in the context of a reference for a preliminary ruling, may provide guidance based on the documents in the file of the case in the main proceedings and on the written and oral observations which have been submitted to it, in order to enable the national court to give judgment. (
48
)
69.
It is also apparent from the case-law that, in the context of indirect discrimination on grounds of sex in relation to working conditions, the employer must prove that there has been no breach of the principle of non-discrimination by providing objective justification for the difference in treatment to the detriment of the disadvantaged group of workers. (
49
)
70.
In their written and oral submissions, Air Nostrum, SEPLA and the Danish and Swedish Governments argued that the difference in treatment with regard to cabin crew is objectively justified by the autonomy of the social partners in negotiating and concluding the collective agreements applying to the workers they represent. UGT, the Public Prosecutor’s Office, the Spanish Government and the Commission do not agree with that approach. (
50
)
71.
Against that background, the question arises as to whether the autonomy of the social partners can, on its own, constitute a sufficient objective justification for a difference in treatment such as that at issue in the main proceedings (Subsection 1) or whether, on the contrary, the differences in the amounts of daily subsistence allowances for two groups of workers must be justified by other objective factors unrelated to any discrimination on grounds of sex (Subsection 2).
(1) The autonomy of the social partners as a sufficient objective justification
72.
I shall examine the objective justification based on the autonomy of the social partners in the context of a single collective bargaining process before examining the justification in the context of separate collective bargaining processes.
(i) Objective justification on the grounds of the autonomy of the social partners in the context of a single collective bargaining process
73.
I would point out at the outset that autonomy in collective bargaining enjoys particular recognition in the legal traditions and national practices of the Member States, thereby constituting the fundamental concept for understanding the development of European labour law, around which the rules of democratic systems of representation are constructed and legal limits on trade union freedom are set. (
51
)
74.
In EU law, the protection of autonomy in collective bargaining is protected in Article 28 of the Charter, which establishes the fundamental right to collective bargaining, to which Article 6 TEU refers through the general recognition of the rights, freedoms and principles set out in the Charter. (
52
) As may be seen in the Court’s case-law, the nature of measures adopted by way of a collective agreement differs from the nature of those adopted unilaterally by way of legislation or regulation by the Member States in that the social partners, when exercising that fundamental right, have taken care to strike a balance between their respective interests. (
53
) The importance of the role played by collective bargaining, now underpinned by the Charter, is therefore undeniable. (
54
)
75.
It follows from that case-law that where the right to collective bargaining enshrined in Article 28 of the Charter is covered by provisions of EU law, it must, within the scope of that law, be exercised in compliance with that law. (
55
) Consequently, when they adopt measures falling within the scope of Directive 2006/54 (which, as I have already stated in my preliminary remarks, gives specific expression in the field of employment and occupation to the principle of non-discrimination on grounds of sex), the social partners must comply with that directive. (
56
) Since the judgment in Defrenne, (
57
) there has been abundant case-law to the effect that the prohibition of discrimination between male and female workers extends to all agreements which are intended to regulate paid labour collectively. (
58
)
76.
To be more precise, it is clear from Article 21(2) of Directive 2006/54 that agreements concluded by the social partners must comply with ‘the provisions of [that] directive and the relevant national implementing measures’. Similarly, under point (b) of the first paragraph of Article 23 of that directive, Member States must take all necessary measures to ensure that ‘provisions contrary to the principle of equal treatment in … collective … agreements … shall be, or may be, declared null and void or are amended’. In that regard, the Court has held on several occasions that collective agreements must, like laws, regulations or administrative provisions, comply with the principle of equal treatment. (
59
)
77.
In my view, it follows that, in the context of Directive 2006/54, the autonomy of the social partners is not sufficient on its own to provide an objective justification for a difference of treatment such as that at issue in the present case.
78.
Moreover, the Court has already held that the fact that EU law precludes a measure appearing in a collective agreement does not interfere with the right to negotiate and conclude collective agreements recognised in Article 28 of the Charter (
60
) since the parties concerned are free to revise the relevant provisions of those agreements. Thus, contrary to what Air Nostrum and SEPLA have submitted, such a revision would involve renegotiating not the entire collective agreement at issue but only the relevant provisions relating to daily subsistence allowances, enabling the balance negotiated between the parties to be maintained.
79.
That being said, and in so far as the case-law I have just examined concerns discrimination that arises, directly or indirectly, from a single collective agreement, I shall now examine the specific feature of the present case, namely objective justification on the grounds of the autonomy of the social partners where there are separate and distinct collective bargaining processes.
(ii) Objective justification on the grounds of the autonomy of the social partners in the context of separate collective bargaining processes
80.
The referring court asks, in essence, whether the fact that, in the main proceedings, the difference in treatment arises from the application of two separate collective agreements negotiated by different trade unions is sufficient on its own as an objective justification for the alleged indirect discrimination under Directive 2006/54.
81.
First, in the context of equal pay, reference should be made to the case which gave rise to the judgment in Enderby, which concerned indirect discrimination on grounds of sex under Article 157 TFEU (formerly Article 119 EEC and Article 141 EC). In that case, the groups concerned were speech therapists and pharmacists, the former being composed almost exclusively of women and the latter mainly of men, and there was a difference in pay disadvantaging speech therapists. First of all, the Court held that the ‘fact that the rates of pay at issue are decided by collective bargaining processes conducted separately for each of the two professional groups concerned, without any discriminatory effect within each group, does not preclude a finding of prima facie discrimination where the results of those processes show that two groups with the same employer and the same trade union are treated differently’. (
61
) It went on to consider that ‘if the employer could rely on the absence of discrimination within each of the collective bargaining processes taken separately as sufficient justification for the difference in pay, he could … easily circumvent the principle of equal pay by using separate bargaining processes’. (
62
) Finally, it ruled that it was insufficient objective justification for the difference in pay to refer to the fact that the respective pay for these two jobs was determined ‘by collective bargaining processes which, although carried out by the same parties, are
distinct, and, taken separately, have in themselves no discriminatory effect’. (
63
)
82.
Admittedly, it is true that, in the case which gave rise to the judgment in Enderby, the difference in treatment arose from the separate collective bargaining processes conducted by the same parties, namely the employer and the trade union representing the two professions concerned. Nevertheless, it is clear from that judgment that the central consideration in the Court’s examination of the justification was the fact that collective bargaining for speech therapists had been conducted ‘separately and independently’ from collective bargaining for pharmacists.
83.
Thus, while in the present case the difference in treatment is due to the fact that the two collective agreements were negotiated with different trade unions, the decisive circumstance is, however, as in the case giving rise to the judgment in Enderby, that distinct collective agreements were negotiated separately and independently. Accordingly, in so far as in both cases the collective agreements were negotiated separately and independently, and therefore concerned different collective bargaining processes, the fact that, in the present case, the collective agreements were negotiated with different trade unions is not sufficient, in my view, to preclude the transposition to the present case of the lessons arising from the judgment in Enderby. (
64
)
84.
Secondly, as the Spanish Government stated in response to a question put by the Court, under Article 89 of the Law on the Workers’ Statute, both the employer and the workers’ representatives are entitled to initiate bargaining and to choose interlocutors to conduct that bargaining. (
65
) According to that government, either party may refuse to enter into bargaining initiated by the other party under the conditions laid down by national law. In that context, the latitude granted to an employer would include the possibility of selecting legitimate interlocutors in compliance with particular rules. (
66
)
85.
Where the workers have initiated bargaining and are authorised to do so, the employer has a duty to enter into bargaining. On that point, the Public Prosecutor’s Office stated at the hearing that the employer could commence bargaining with the workers’ representatives ‘while freely deciding whether or not to agree to reach an agreement on specific issues’.
86.
Admittedly, even if, as the referring court assumes, each group of trade union representatives in each bargaining process gave some claims priority over others vis-à-vis Air Nostrum, that court nevertheless notes that the Cabin Crew Agreement had already been signed when the airline negotiated the Flight Crew Agreement, and it was therefore aware of the amounts set for the cabin crew’s daily subsistence allowances. It can therefore readily be considered that the airline was aware that the difference in treatment in respect of working conditions resulting from the payment of the daily subsistence allowances in question placed cabin crew at a comparative disadvantage, contrary to the national legislation transposing Directive 2006/54 and accordingly to that directive itself.
87.
Thirdly, it is certainly true that at first sight, the rejection of Air Nostrum’s justification could be seen as possibly leading to a collective agreement being applied, albeit indirectly, to workers whose trade union representatives had not negotiated that agreement, nor, a fortiori, concluded it.
88.
However, if the autonomy of the social partners were accepted as the sole objective justification for discrimination such as that in the present case, that would, in my view, be tantamount to accepting the absence of any indirect discrimination in all cases where there were distinct collective agreements, including in cases concerning working conditions. Indeed, as the Court’s case-law makes plain, if the employer could rely on the absence of discrimination within each of the collective bargaining processes taken separately as justification for a difference in working conditions, he or she could easily circumvent the fundamental principle of equal treatment by means of separate bargaining processes. (
67
)
89.
Fourthly, as the Commission remarked in its written observations, where there are no specific details of the conduct of the bargaining process, accepting that the autonomy of the social partners and the possibility for the parties to adopt separate negotiating strategies may be relied on in general terms could, at the very least, obscure the fact that, even if trade unions strive to improve the working conditions of all workers, both employers and trade unions may have unconscious prejudices leading them to underestimate the needs of female workers in comparison with those of male workers and, consequently, to accept different conditions for groups composed predominantly of women. (
68
)
90.
In any event, even if the existence of two separate collective agreements might be considered at first sight as a possible objective justification for the difference in treatment in question, it should be remembered that, in so far as the Cabin Crew Agreement concerns mostly women and the Flight Crew Agreement mostly men, it is not possible to identify, in the context of indirect discrimination, the precise fact which causes the comparative disadvantage, since the justification must be linked to an aim that is different
and
unrelated to any discrimination on grounds of sex. (
69
)
91.
It follows from all the foregoing that, if point (b) of the first paragraph of Article 23 of Directive 2006/54 is not to be rendered devoid of any useful effect, the autonomy of the social partners in the context of separate and distinct collective bargaining processes is not on its own an objective aim unrelated to any discrimination based on sex and consequently does not suffice on its own as an objective justification of a difference in treatment such as that in the present case.
(2) The existence of other objective factors unrelated to any discrimination on grounds of sex to justify the difference in treatment at issue
92.
It seems to me important to distinguish between, on the one hand, the finding that the fact that the inequality of treatment arises from the application of two separate collective agreements might in itself constitute a sufficient basis to justify a difference of treatment on grounds of sex and, on the other hand, the finding that that justification could combine with other factors to form an objective justification unrelated to any discrimination on grounds of sex under Directive 2006/54.
93.
With regard to the latter fact, as the Court’s case-law makes plain, the national court may take account of the existence of the two collective agreements in order to assess whether there are differences between the daily subsistence allowances of the two groups concerned and whether those differences are due to other objective factors unrelated to any discrimination on grounds of sex. (
70
)
94.
However, it should be noted that such factors are not apparent either from the order for reference or from Air Nostrum’s observations. In that regard, I note that, even supposing that the justification put forward seeks to pursue a legitimate aim, it follows from the Court’s case-law that a mere generalisation is insufficient to show that the aim of the measure at issue is unrelated to any discrimination on grounds of sex. (
71
)
95.
Conversely, if the employer provides specific and convincing evidence of the fact that the difference in treatment in fact stems from a legitimate aim, and not from the difference in sex, it will be for the referring court to assess whether that is indeed the case. As the Commission has rightly observed, such evidence may relate in particular to the respective priorities of the trade unions representing the workers.
96.
In those circumstances, and as is apparent from the foregoing, it is not sufficient for the employer to refer to the fact that there were two separate collective bargaining processes; the employer must prove in this particular case that each group’s priorities were different, that they were negotiated genuinely and independently and that the parties actually negotiated in accordance with their respective priorities, emphasising some issues while being flexible on others so as to reach an agreement which took account of the interests of both parties. On that point, it seems to me important for the referring court to ascertain whether the seemingly disadvantaged group, in full knowledge of the differences in the amounts of the daily subsistence allowances in question, accepted those differences while in return giving priority to other factors relating, in particular, to working conditions, such as the quality of hotels or the number of days of annual leave.
(b)
Whether the practice at issue in the main proceedings is appropriate and necessary to attain the aim pursued
97.
In view of my analysis, there is no need to examine the question whether the practice at issue is capable of achieving the aim pursued. However, I should like to point out that, if evidence of a legitimate aim is adduced, the referring court will have to ascertain whether the means of achieving that legitimate aim are appropriate and necessary for the purposes of Article 2(1)(b) of Directive 2006/54.
98.
When conducting such an assessment, it would seem to me appropriate for the referring court to take into consideration factors such as the plausibility of information concerning the daily subsistence allowances at issue provided by the employer, in particular whether or not those allowances fulfil their purpose of covering meal costs incurred during work-related journeys.
V. Conclusion
99.
Having regard to all the foregoing considerations, I propose that the Court reply to the question referred by the Audiencia Nacional (National High Court, Spain) as follows:
Article 14(1)(c) of Directive 2006/54/EC of the European Parliament and of the Council of 5 July 2006 on the implementation of the principle of equal opportunities and equal treatment of men and women in matters of employment and occupation
must be interpreted as precluding a practice whereby an airline pays cabin crew, the majority of whom are women, a daily subsistence allowance to cover the cost of meals during work-related travel of a lower amount than the allowance paid for the same expenses to flight crew, the majority of whom are men, where that inequality of treatment arises from the application of two separate collective agreements negotiated by the employer and different trade unions.
(
1
)	Original language: French.
(
2
)	Directive of the European Parliament and of the Council of 5 July 2006 on the implementation of the principle of equal opportunities and equal treatment of men and women in matters of employment and occupation (OJ 2006 L 204, p. 23).
(
3
)	BOE No 255 of 24 October 2015, p. 100224.
(
4
)	‘Tripulantes de cabina de pasajeros’.
(
5
)	BOE No 12 of 14 January 2019, p. 2519, available at: https://www.boe.es/eli/es/res/2018/12/18/(14).
(
6
)	BOE No 134 of 13 May 2020, p. 32752, available at: https://www.boe.es/eli/es/res/2020/03/10/(12).
(
7
)	This also follows from the judgment of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560).
(
8
)	On the position of the Public Prosecutor’s Office, see point 29 below. At the hearing, the Public Prosecutor’s Office and the Spanish Government explained the reasons for maintaining the proceedings before the referring court.
(
9
)	See Lenaerts, K. and Gutièrrez-Fons, J.A., ‘Epilogue. High Hopes: Autonomy and the Identity of the EU’, European Papers, Vol. 8, No 3, 2023, pp. 1495 – 1511.
(
10
)	See, in particular, judgment of 5 July 2017, Fries (C‑190/16, EU:C:2017:513, paragraph 29).
(
11
)	As a reminder, Directive 2006/54 incorporates particular elements of the Court’s case-law and consolidates the existing provisions of various directives relating to equality between women and men, namely Council Directive 75/117/EEC of 10 February 1975 on the approximation of the laws of the Member States relating to the application of the principle of equal pay for men and women (OJ 1975 L 45, p. 19), Council Directive 76/207/EEC of 9 February 1976 on the implementation of the principle of equal treatment for men and women as regards access to employment, vocational training and promotion, and working conditions (OJ 1976 L 39, p. 40), Council Directive 86/378/EEC of 24 July 1986 on the implementation of the principle of equal treatment for men and women in occupational social security schemes (OJ 1986 L 225, p. 40), and Council Directive 97/80/EC of 15 December 1997 on the burden of proof in cases of discrimination based on sex (OJ 1998 L 14, p. 6).
(
12
)	See point 18 above.
(
13
)	See judgments of 8 May 2019, Villar Láiz (C‑161/18, EU:C:2019:382, paragraph 37 and the case-law cited), and of 21 January 2021, INSS (C‑843/19, EU:C:2021:55, paragraph 24). Those judgments signal a change in the definition of the concept of ‘indirect discrimination’ compared with the earlier case-law, according to which ‘indirect discrimination arises where a national measure, albeit formulated in neutral terms, works to the disadvantage of far more women than men’ (emphasis added). See, in particular, judgments of 14 April 2015, Cachaldora Fernández (C‑527/13, EU:C:2015:215, paragraph 28), and of 9 November 2017, Espadas Recio (C‑98/15, EU:C:2017:833, paragraph 38 and the case-law cited).
(
14
)	The measure at issue is the employer’s practice of paying cabin crew and flight crew daily subsistence allowances in the different amounts specified in two separate collective agreements.
(
15
)	On the influence of the US ‘disparate impact’ doctrine on indirect discrimination in EU social law, see, inter alia, Tobler, C., Indirect Discrimination. A Case Study into the Development of the Legal Concept of Indirect Discrimination under EC Law, Intersentia, Antwerp and Oxford, 2005, pp. 91 – 96 and 235, and Mulder, J., Indirect sex discrimination in employment. Theoretical analysis and reflections on the CJEU case-law and national application of the concept of indirect sex discrimination, Directorate-General for Justice and Consumers (EC), 2021, p. 44. See, in that respect, judgment of 31 March 1981, Jenkins (96/80, EU:C:1981:80, p. 925, paragraph 13). See also the Opinion of Advocate General Warner in Jenkins (96/80, EU:C:1981:21, pp. 936 and 937) and the Opinion of Advocate General Poiares Maduro in Coleman (C‑303/06, EU:C:2008:61, point 19).
(
16
)	As academic commentators have emphasised, this involves a more qualitative assessment of a measure’s potential adverse impact on persons satisfying a particular criterion compared with other persons. The definition of ‘indirect discrimination’ also makes it possible to address indirect discrimination based on criteria for which there are no quantitative data. See Miné, M., ‘Les concepts de discrimination directe et indirecte’, ERA Forum, Vol. 4, 2003, pp. 30 – 44, in particular pp. 38 – 39, and Tridimas, T., The General Principles of EU Law, Oxford University Press, Oxford, 2005, second edition, pp. 67 – 72. See also footnote 42 below.
(
17
)	It is clear from the order for reference that Article 93 of, and Annex I to, the Cabin Crew Agreement and Article 16(19) of the Flight Crew Agreement are apparently neutral since these provisions apply to both male and female members of cabin crew and flight crew respectively.
(
18
)	See, in particular, judgments of 27 October 1998, Boyle and Others (C‑411/96, EU:C:1998:506, paragraph 39); of 21 October 1999, Lewen (C‑333/97, EU:C:1999:512, paragraph 36); of 30 March 2004, Alabaster (C‑147/02, EU:C:2004:192, paragraph 45), and of 16 July 2009, Gómez-Limón Sánchez-Camacho (C‑537/07, EU:C:2009:462, paragraph 56).
(
19
)	See, in particular, Tobler, C., Limits and potential of the concept of indirect discrimination, Office for Official Publications of the European Communities, Luxembourg, 2008, pp. 24 and 26. As regards the general principle of equal treatment, see, in particular, judgment of 4 May 2023, Glavna direktsia Pozharna bezopasnost i zashtita na naselenieto (Night work) (C‑529/21 to C‑536/21 and C‑732/21 to C‑738/21, EU:C:2023:374, paragraph 52).
(
20
)	The concept of ‘indirect discrimination’ was set out for the first time in the judgment of 13 May 1986, Bilka-Kaufhaus (170/84, EU:C:1986:204), concerning access to a company pension scheme. See, in that regard, Prechal, S., ‘Combatting Indirect Discrimination in Community Law Context’, Legal Issues of European Integration, Vol. 19, No 1, 1993, pp. 81 – 97, in particular p. 84.
(
21
)	On the development of the definition of ‘indirect discrimination in EU law’, see Ellis, E. and Watson, P., EU Anti-Discrimination Law, second edition, Oxford European Union Law Library, Oxford, 2012, pp. 148 – 155.
(
22
)	See points 38 and 39 above.
(
23
)	Article 2(1)(a) of Directive 2006/54 defines ‘direct discrimination’ as ‘where one person is treated less favourably on grounds of sex than another is, has been or would be treated in a comparable situation’.
(
24
)	With regard to the requirement of comparability of situations in the context of direct discrimination, the Court has explained that, on the one hand, it is required not that the situations be identical but only that they be comparable and, on the other hand, the assessment of that comparability must be carried out not in a global and abstract manner, but in a specific and concrete manner in the light of the benefit concerned. See, in particular, judgments of 12 December 2013, Hay (C‑267/12, EU:C:2013:823, paragraph 33), and of 19 July 2017, Abercrombie & Fitch Italia (C‑143/16, EU:C:2017:566, paragraph 25).
(
25
)	See footnote 16 above (emphasis added).
(
26
)	See, to that effect, in particular, Tobler, C., Indirect discrimination under Directives 2000/43 and 2000/78, Leiden University, Leiden, p. 100, as well as Tobler, C., Limits and potential of the concept of indirect discrimination, op. cit., p. 48.
(
27
)	See, to that effect, in particular, Mulder, J., Indirect sex discrimination in employment, op. cit., pp. 50 and 51, and Tobler, C., Indirect discrimination under Directives 2000/43 and 2000/78, op. cit., pp. 23, 99 and 100. It should be noted that the factors to be examined when performing the comparison are not the same as those to be taken into account in determining the legitimacy of the justification relied on. Thus, the existence of one or of several collective agreements is a factor that may be taken into account in assessing whether differences between the daily subsistence allowances in question are due to objective factors unrelated to any discrimination on grounds of sex. See, inter alia, to that effect, judgment of 31 May 1995, Royal Copenhagen (C‑400/93, EU:C:1995:155, paragraph 46). See points 92 et seq. below.
(
28
)	See, to that effect, in particular, Mulder, J., Indirect sex discrimination in employment, op. cit., p. 12. However, as regards the principle of equal pay, which is not at issue in the present case, the groups of workers to be compared must perform work of equal value.
(
29
)	See Mulder, J., Indirect sex discrimination in employment, op. cit., pp. 12 and 50.
(
30
)	See, to that effect, Tobler, C., Limits and potential of the concept of indirect discrimination, op. cit., in particular footnote 127.
(
31
)	On the importance of identifying the comparator in the context of indirect discrimination, see, in particular, Ellis, E. and Watson, P., EU Anti-Discrimination Law, op. cit., p. 152.
(
32
)	See, in particular, judgment of 24 February 2022, TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2022:120, paragraphs 49 and 50 and the case-law cited), in which the Court held that ‘the argument that the situation of domestic workers is not comparable to that of other employed workers … which was put forward … to support the contention that there is no such indirect discrimination, is irrelevant in that regard. As the Advocate General stated in point 47 of his Opinion, unlike the case which gave rise to the judgment of 26 June 2018, MB (Change of gender and retirement pension) (C‑451/16, EU:C:2018:492), …, the national provision at issue in the main proceedings does not constitute direct discrimination on grounds of sex which could be disputed by alleging that the situation of domestic workers was not comparable to that of other employed workers.’ See, in that respect, my Opinion in TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2021:777, point 47).
(
33
)	In the matter of equal pay, the groups of workers being compared must perform work of equal value. See footnote 28 above.
(
34
)	See, in that regard, point 35 above.
(
35
)	The Commission pointed out at the hearing that daily subsistence allowances were not regarded as pay in the two collective agreements in question.
(
36
)	I would recall that the method of identifying the comparator for the purposes of the comparison in the context of indirect discrimination is not exactly the same as in the case of direct discrimination. In that regard, see points 48 and 49 above.
(
37
)	See, in that regard, in particular, Mulder, J., Indirect sex discrimination in employment, op. cit., p. 12.
(
38
)	In other words, the people subject to comparison (the groups compared) are cabin crew, who are predominantly women, and flight crew, who are predominantly men. That comparison (the tertium comparationis) relates to the amount of the daily subsistence allowances at issue in the main proceedings.
(
39
)	In the present case, the identification concerns only the provisions relating to daily subsistence allowances in each collective agreement, not other provisions of those agreements.
(
40
)	See, in particular, judgment of 24 February 2022, TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2022:120, paragraph 41 and the case-law cited). On the burden of proof, see Article 19 of Directive 2006/54. As the Court has held, it is the person who considers himself or herself to have been wronged because the principle of equal treatment has not been applied to him or her who must initially establish the facts from which it may be presumed that there has been direct or indirect discrimination. It is only if that person has established such facts that it is then for the defendant to prove that there has been no breach of the principle of non-discrimination. See judgment of 19 April 2012, Meister (C‑415/10, EU:C:2012:217, paragraph 36). See, in that regard, Burri, S. and Prechal, S., L’égalité des genres dans le droit de l’Union européenne, European Commission, Luxembourg, 2008, p. 17.
(
41
)	See, in that respect, judgment of 31 March 1981, Jenkins (96/80, EU:C:1981:80, p. 925, paragraph 13), and Opinion of Advocate General Warner in Jenkins (96/80, EU:C:1981:21, pp. 936 and 937).
(
42
)	See judgment of 21 January 2021, INSS (C‑843/19, EU:C:2021:55, paragraph 27 and the case-law cited). It is worth noting that indirect discrimination may be established by any means, not only on the basis of statistical evidence. See, in particular, judgments of 8 May 2019, Villar Láiz (C‑161/18, EU:C:2019:382, paragraph 46), and of 3 October 2019, Schuch-Ghannadan (C‑274/18, EU:C:2019:828, paragraph 54). In that respect, it bears noting that Directive 2006/54 does not refer to ‘quantitative elements in the examination of indirect discrimination. Moreover, that definition adopts a qualitative approach, namely that it is necessary to verify whether the national provision at issue is likely, by its nature, to put persons of one sex at a “particular disadvantage” compared with persons of the other sex’. See the Opinion of Advocate General Rantos in Joined Cases IK and CM (C‑184/22 and C‑185/22, EU:C:2023:879, point 36).
(
43
)	Here, the provisions of the relevant collective agreements.
(
44
)	See, in particular, to that effect, judgments of 24 September 2020, YS (Occupational pensions of managerial staff) (C‑223/19, EU:C:2020:753, paragraph 52 and the case-law cited), and of 21 January 2021, INSS (C‑843/19, EU:C:2021:55, paragraph 26). See also, to that effect, judgment of 8 May 2019, Villar Láiz (C‑161/18, EU:C:2019:382, paragraphs 39 and 45).
(
45
)	More specifically, the order for reference shows that the amount of the daily subsistence allowance for cabin crew varies between EUR 37.06 and EUR 59.06 depending on whether the journey is national or international. On that point, the Spanish Government explains in its written observations that cabin crew receive a full allowance if they work more than four full hours. If cabin crew are on duty for four hours or less, they receive half a daily subsistence allowance. By contrast, for journeys of the same type, the daily subsistence allowances for flight crew are between EUR 65 and EUR 100 respectively. In that case, the Spanish Government states in its written observations that, under certain travel conditions, supplementary coefficients may be applied to the daily subsistence allowances paid to flight crew that multiply those allowances by 1.2 to 2.
(
46
)	See, to that effect, judgment of 8 May 2019, Villar Láiz (C‑161/18, EU:C:2019:382, paragraph 47).
(
47
)	Thus, where the situations examined are not comparable, the difference in treatment does not constitute direct discrimination. Moreover, direct discrimination can only be justified on specific grounds expressly provided for by law. See in that respect the case-law cited in footnote 32 above. See also my Opinion in TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2021:777, point 47 and footnote 21).
(
48
)	See, to that effect, judgments of 24 September 2020, YS (Occupational pensions for managerial staff) (C‑223/19, EU:C:2020:753, paragraph 58), and of 24 February 2022, TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2022:120, paragraph 51 and the case-law cited).
(
49
)	See, to that effect, judgment of 28 February 2013, Kenny and Others (C‑427/11, EU:C:2013:122, paragraph 41).
(
50
)	See point 29 above.
(
51
)	See Sciarra, S., ‘The evolution of collective bargaining: observations on a comparison in the countries of the European Union’, Comparative Labor Law & Policy Journal, Vol. 29, No 1, pp. 1 – 28, in particular p. 7. On the importance of collective bargaining, see, in particular, the Opinion of Advocate General Jacobs in Albany (C‑67/96, C‑115/97 and C‑219/97, point 181), and the Opinion of Advocate General Cruz Villalón in Prigge and Others (C‑447/09, EU:C:2011:321, points 41 to 46).
(
52
)	See Rodière, P., ‘Droit de négociation et d’actions collectives’, Charte des droits fondamentaux de l’Union européenne, Picod, F., and Van Drooghenbroeck, S., (eds.), second edition, Bruyland, Paris, 2018, pp. 621 to 646.
(
53
)	Judgment of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560, paragraph 66 and the case-law cited). In particular, as regards Directive 2006/54, the important role of collective agreements as an integral part of the legal order of the Member States in ‘the effective implementation of the principle of equal treatment’ is apparent from Article 33 thereof. Thus, in compliance with Article 21(1) of that directive, ‘Member States shall … take adequate measures to promote social dialogue between the social partners with a view to fostering equal treatment’.
(
54
)	At EU level, dialogue between the social partners is recognised in Article 155 TFEU.
(
55
)	Judgments of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560, paragraph 67); of 11 December 2007, International Transport Workers’ Federation and Finnish Seamen’s Union (C‑438/05, EU:C:2007:772, paragraph 44); and of 18 December 2007, Laval un Partneri (C‑341/05, EU:C:2007:809, paragraph 91).
(
56
)	See, to that effect, judgments of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560, paragraph 68), and of 27 October 1993, Enderby (C‑127/92, ‘the judgment in Enderby, EU:C:1993:859, paragraph 22).
(
57
)	Judgment of 8 April 1976 (43/75, EU:C:1976:56, paragraph 39).
(
58
)	See, in particular, judgments of 27 June 1990, Kowalska (C‑33/89, EU:C:1990:265, paragraph 12); of 18 November 2004, Sass (C‑284/02, EU:C:2004:722, paragraph 25); of 9 December 2004, Hlozek (C‑19/02, EU:C:2004:779, paragraph 43); of 18 November 2020, Syndicat CFTC (C‑463/19, EU:C:2020:932, paragraph 48); and of 3 June 2021, Tesco Stores (C‑624/19, EU:C:2021:429, paragraph 21 and the case-law cited).
(
59
)	With regard to point (b) of the first paragraph of Article 16 of Council Directive 2000/78/EC of 27 November 2000 establishing a general framework for equal treatment in employment and occupation (OJ 2000 L 303, p. 16), which is equivalent to point (b) of the first paragraph of Article 23 of Directive 2006/54, see judgments of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560, paragraph 63); of 13 September 2011, Prigge and Others (C‑447/09, EU:C:2011:573, paragraph 49); and of 28 February 2013, Kenny and Others (C‑427/11, EU:C:2013:122, paragraph 47).
(
60
)	Judgment of 8 September 2011, Hennigs and Mai (C‑297/10 and C‑298/10, EU:C:2011:560, paragraph 78).
(
61
)	Judgment of 27 October 1993, Enderby (C‑127/92, EU:C:1993:859, paragraph 22) (emphasis added). On the adverse effect, see point 40 above.
(
62
)	Judgment of 27 October 1993, Enderby (C‑127/92, EU:C:1993:859, paragraph 22).
(
63
)	Judgment of 27 October 1993, Enderby (C‑127/92, EU:C:1993:859, paragraph 23). Emphasis added.
(
64
)	Thus, in order to justify the difference in treatment on grounds of sex, ‘it is not sufficient … for the common employer to refer to the existence of different collective agreements even if, considered separately, neither discriminates on grounds of sex’; see the Opinion of Advocate General Lenz in Enderby (C‑127/92, EU:C:1993:313, point 50).
(
65
)	On that point, the Spanish Government has explained that Article 89(1) of the Law on the Workers’ Statute allows ‘workers’ or employers’ representatives’ (who, under Article 87 of that law, must be authorised to negotiate a collective agreement) to initiate bargaining by notifying the other party in writing. The party to whom the notification is sent may refuse to enter into bargaining only on legal grounds or on the grounds of an existing agreement, or where the bargaining does not concern the revision of an agreement that has already expired.
(
66
)	Under Article 89(2) of the Law on the Workers’ Statute, the bargaining committee is to be set up within a maximum of one month of receipt of the notification. The party to whom the notification is sent must then respond to the bargaining proposal and the two parties must draw up the bargaining schedule or plan.
(
67
)	See, to that effect, judgment of 27 October 1993, Enderby (C‑127/92, EU:C:1993:859, paragraph 22).
(
68
)	As academic commentators have noted, ‘the rejection of separate collective bargaining processes as justification for indirect sex discrimination supports equality of opportunity, since merely to ask whether arriving at two different levels of pay was due to the operation of two different processes is insufficient. It is necessary to look behind those processes and ask why one collective agreement was able to arrive at a more favourable result than the other’ in respect of the same measure. See Hervey, T.K., ‘EC Law on Justifications for Sex Discrimination in Working Life’, Collective Bargaining, Discrimination, Social Security and European Integration, Bulletin of Comparative Labour Relations, Vol. 48, Kluwer Law International, 2003, pp. 103 – 152, in particular p. 133. See also Vogel-Polsky, E., ‘Genre et droit: les enjeux de la parité’, Cahiers du GEDISST (Groupe d’étude sur la division sociale et sexuelle du travail), No 17, 1996, ‘Principes et enjeux de la parité’, pp. 11 to 31: ‘The occupational segregation … of women in the economy and the world of work has its origins in gendered social relationships as a whole [or] in pervasive stereotypes articulated by culture, education, the school system, family, the media …’. See my Opinion in TGSS (Domestic worker unemployment) (C‑389/20, EU:C:2021:777, point 78).
(
69
)	In respect of a disadvantaged group of part-time workers consisting mainly of women, see judgment of 10 March 2005, Nikoloudi (C‑196/02, EU:C:2005:141, paragraph 51). See, to that effect, in particular, Tobler, C., Limits and potential of the concept of indirect discrimination, op. cit., p. 37.
(
70
)	See, in particular, judgments of 31 May 1995, Royal Copenhagen (C‑400/93, EU:C:1995:155, paragraph 46), and of 28 February 2013, Kenny and Others (C‑427/11, EU:C:2013:122, paragraph 49).
(
71
)	See, to that effect, judgment of 10 March 2005, Nikoloudi (C‑196/02, EU:C:2005:141, paragraph 52 and the case-law cited).