EX-4.2



 Exhibit 4.2 
 SIXTH AMENDED AND RESTATED  
 STOCK RESTRICTION AND CO-SALE
AGREEMENT 
 SIXTH AMENDED AND RESTATED STOCK RESTRICTION AND CO-SALE AGREEMENT made this 22nd day of December, 2011 by and among (i) KAYAK Software
Corporation, a Delaware corporation (the “Company”), (ii) holders of Common Stock, or options or warrants to acquire Common Stock whose names are set forth under the heading “Holders” on Schedule I
hereto and each person who shall, after the date hereof, acquire shares of Common Stock (or options or warrants to acquire Common Stock) and join in and become a party to this Agreement by executing and delivering to the Company an Instrument of
Accession in the form of Schedule II hereto (the persons described in this clause (ii) being referred to collectively as the “Holders” and singularly as a “Holder”) and (iii) those
persons whose names are set forth under the heading “Investors” on Schedule I hereto (the persons described in this clause (iii) being referred to collectively as the “Investors”). The Holders and
Investors are collectively referred to herein as the “Stockholders”. 
 WITNESSETH: 

WHEREAS, the Holders currently own shares of the Company’s Common Stock, par value $.001 per share (the “Common
Stock”) and the Purchaser Warrants (as defined below); and 
 WHEREAS, certain of the Investors have
heretofore purchased from the Company an aggregate of (i) six million six hundred thousand (6,600,000) shares of the Company’s Series A Convertible Preferred Stock, par value $.001 per share (the “Series A
Stock”), (ii) one million one hundred seventy six thousand fifty one (1,176,051) shares of the Company’s Series A-1 Convertible Preferred Stock, par value $.001 per share (the “Series A-1 Stock”,
and collectively with the Series A Stock, the “Series A Preferred Stock”), (iii) four million nine hundred eighty nine thousand three hundred eight (4,989,308) shares of the Company’s Series B Convertible
Preferred Stock, par value $.001 per share (the “Series B Stock”), (iv) two million one hundred thirty eight thousand two hundred seventy five (2,138,275) shares of the Company’s Series B-1 Convertible
Preferred Stock, par value $.001 per share (the “Series B-1 Stock”, and collectively with the Series B Stock, the “Series B Preferred Stock”), (v) three million eight hundred fifty five thousand
one hundred eighty (3,855,180) shares of the Company’s Series C Convertible Preferred Stock, par value $.001 per share (the “Series C Stock”) and (vi) eight million eight thousand eight hundred forty two
(8,008,842) shares of the Company’s Series D Convertible Preferred Stock, par value $.001 per share (the “Series D Stock”, and collectively with the Series A Preferred Stock, the Series B Preferred Stock and the
Series C Stock, the “Convertible Preferred Stock”); 
 WHEREAS, certain of the Investors
previously entered into that certain Fifth Amended and Restated Stock Restriction and Co-Sale Agreement, dated as of December 20, 2007 (together with all exhibits thereto, the “Prior Agreement”), in connection with a
certain Series D Convertible Stock Purchase Agreement dated as of December 20, 2007 (the “Purchase Agreement”), by and among certain of the Investors and the Company pursuant to which the Company issued the Series D
Stock to such Investors; and 

  
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 WHEREAS, the Company and the Requisite Investors have mutually agreed to amend and
restate the Prior Agreement in its entirety. 
 NOW, THEREFORE, for good and valuable consideration, the receipt and
legal sufficiency of which is hereby acknowledged, the Company, the Holders and the Investors hereby agree to amend and restate the Prior Agreement in its entirety as follows: 
 1. Prohibited Transfers. The Holders shall not sell, assign, transfer, pledge, hypothecate, mortgage or dispose of, by gift or otherwise, or in any way encumber, all or any part of the Shares (as
hereinafter defined) owned by them except in compliance with the terms of this Agreement. For purposes of this Agreement, the term “Shares” shall mean and include all shares of Common Stock (excluding shares of Common Stock issued upon
conversion of the Convertible Preferred Stock) and the Warrants to purchase shares of Common Stock issued or issuable pursuant to the terms of the Interactive Marketing Agreement between the Company and America Online, Inc. dated as of
November 10, 2004 (the “Purchaser Warrants”). The Company shall not transfer on its books any Shares which are subject to this Agreement unless the provisions hereof have been complied with in full. Any purported
transfer by a Holder of Shares without full compliance with the provisions of this Agreement shall be null and void. 
 2.
Right of First Refusal on Dispositions by the Holders. If at any time any Holder wishes to sell, assign, transfer or otherwise dispose of any or all Shares owned by such Holder pursuant to the terms of a bona fide offer received from a third
party, such Holder shall submit a written offer to sell such Shares to the Company and the Investors on terms and conditions, including price, not less favorable to the Company and the Investors than those on which such Holder proposes to sell such
Shares to such third party (the “Offer”). The Offer shall disclose the identity of the proposed purchaser or transferee, the Shares proposed to be sold or transferred (the “Offered
Shares”), the agreed terms of the sale or transfer, including price, and any other material facts relating to the sale or transfer. The Investors shall, subject to the first sentence of Section 3, have the right to purchase,
on the same terms and conditions set forth in the Offer, that portion of the Offered Shares to be determined in the manner set forth herein. Each Investor shall have the right to purchase up to that number of Offered Shares as shall be equal to the
aggregate Offered Shares multiplied by a fraction, the numerator of which is the number of shares of Common Stock issued or issuable to such Investor upon the conversion of all shares of Convertible Preferred Stock held by such Investor together
with the number of shares of Common Stock actually issued upon the exercise of Purchaser Warrants and held by such Investor (the “Conversion Shares”) and the denominator of which is the aggregate number of Conversion Shares
held by all Investors. The number of Offered Shares each Investor or Qualified Transferee, as that term is defined below, is entitled to purchase under this Section 2 shall be referred to as such Investor’s “Pro Rata Fraction.”
Each Investor shall have the right to transfer its right to any Pro Rata Fraction or part thereof to any Qualified Transferee (as defined below). In the event an Investor does not wish to purchase or to transfer its right to purchase its Pro Rata
Fraction, then any Investors who so elect shall have the right to purchase, on a pro rata basis with any other Investors who so elect, any Pro Rata Fraction not purchased by an Investor or Qualified Transferee. Each Investor shall act upon
the Offer as soon as practicable after receipt of the Offer, and in all events within fifteen (15) days after receipt of the Offer. Each Investor shall have the right to accept the Offer as to all or part of the Offered Shares. In the event
that an Investor shall elect to purchase all or part of the Offered Shares covered by the 

  
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Offer, said Investor shall individually communicate in writing such election to purchase to whichever of the Holders has made the Offer, which communication shall be delivered in accordance with
Section 8 below and shall, when taken in conjunction with the Offer be deemed to constitute a valid, legally binding and enforceable agreement for the sale and purchase of the Offered Shares covered thereby. 

If the Investors do not exercise their right to purchase all of the Offered Shares from a Holder within said fifteen-day period, such
Holder shall promptly notify the Company in writing (the “Company Notice”) as to the number of Offered Shares which the Investors shall not have agreed to purchase (the “Remaining Shares”). Subject to
the approval of the holders of at least fifty eight percent (58%) of the votes attributable to all outstanding shares of Convertible Preferred Stock (voting as a separate class on an as-converted to Common Stock basis) (the
“Requisite Investors”), the Company shall have the right to purchase all of the Remaining Shares on the same terms and conditions as set forth in the Offer. If the Company elects to purchase any Remaining Shares, it shall
notify the Holder within fifteen days after receipt of the Company Notice (the “Final Date”). 
 For
purposes of this Section 2, a “Qualified Transferee” of an Investor shall mean any person (i) who is an Investor, (ii) who is an “affiliated person” of an Investor, as that term is defined in the Investment Company
Act of 1940, (iii) who is a partner of an Investor, or (iv) who previously acquired at least 250,000 shares of Convertible Preferred Stock (as adjusted for stock splits, stock dividends, reclassifications, recapitalizations or other
similar events). 
 3. Right of Participation in Sales by Holders. In the event that the Investors and the Company do not
exercise their rights under Section 2 with respect to all of the Offered Shares, the transferring Holder may, subject to the provisions of this Section 3, sell, assign, transfer or otherwise dispose of all of the Offered Shares to the
third party named in the Offer (the “Purchaser”). Before any such sale, assignment, transfer or other disposition, each Investor shall have the right to require, as a condition to such sale or disposition, that the Purchaser
purchase from said Investor at the same price per Share (which shall be calculated on a Common Stock equivalent basis if the Stock (as defined in Section 5) to be sold by an Investor is of a different class or series of stock from that of the
Shares) and on the same terms and conditions as involved in such sale or disposition by the Holder up to a number of shares of Stock as is equal to the product of (x) the number of Shares proposed to be sold by the Holder, times (y) a
fraction, the numerator of which is the number of Conversion Shares held by such Investor and the denominator of which is the aggregate number of Conversion Shares held by all Investors electing to participate in the sale pursuant to this
Section 3 plus the number of shares of Stock owned by the selling Holder (calculated on an as-converted to Common Stock basis). Each Investor wishing so to participate in any such sale or disposition shall notify the selling Holder of such
intention as soon as practicable after receipt of the Offer made pursuant to Section 2, and in all events within fifteen (15) days after receipt of the Investor Notice. In the event that an Investor shall elect to participate in such sale
or disposition, said Investor shall individually communicate such election to the selling Holder, which communication shall be delivered in accordance with Section 8 below. The Holder and/or each participating Investor shall sell to the
Purchaser all, or at the option of the Purchaser, any part of the Stock proposed to be sold by them at not less than the price and upon other terms and conditions, if any, not more favorable to the


  
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Purchaser than those originally offered; provided, however, that any purchase of less than all of such Stock by the Purchaser shall be made from the Holder and/or each participating
Investor pro rata based on the number of shares such Holder and/or Investors would otherwise be entitled to sell to such Purchaser pursuant to this Section 3. The selling Holder or Investor shall use his or its reasonable best efforts to obtain
the agreement of the Purchaser to the participation of the participating Investors in the contemplated sale, and shall not sell any Stock to such Purchaser if such Purchaser declines to permit the participating Investors to participate pursuant to
the terms of this Section 3. The provisions of this Section 3 shall not apply to the sale of any Shares by a Holder to an Investor pursuant to an Offer under Section 2. 

 

	 	4.	Permitted Transfers. 


(i) Anything herein to the contrary notwithstanding, the provisions of Sections 1, 2 and 3 shall not apply to: (a) any transfer of
Shares by a Holder by gift or bequest or through inheritance to, or for the benefit of, any member or members of his or her immediate family (which shall include any spouse, children or grandchildren) or to a trust, partnership or limited liability
company for the benefit of such Holder or such members of his or her immediate family; (b) any transfer of Shares by a Holder to a trust in respect of which he or she serves as trustee, provided that the trust instrument governing said trust
shall provide that such Holder, as trustee, shall retain sole and exclusive control over the voting and disposition of said Shares until the termination of this Agreement; (c) any sale of Common Stock in a public offering pursuant to a
registration statement filed by the Company with the Securities and Exchange Commission; (d) any repurchase of shares of Common Stock by the Company from officers, employees, directors or consultants of the Company which are subject to restrictive
stock purchase agreements under which the Company has the option to repurchase such shares at cost (or a lesser amount) upon the occurrence of certain events; and (e) any repurchase of Shares by the Company pursuant to the Restricted Stock
Agreement, dated as of March 2, 2004, by and between the Company and Daniel Stephen Hafner, and the Restricted Stock Agreement, dated as of March 2, 2004, by and between the Company and Paul English (collectively, the “Founder
Stock Agreements”). 
 (ii) In the event of any such transfer, other than pursuant to subsections (i)(c),
(d) and (e) of this Section 4, the transferee of the Shares shall hold the Shares so acquired with all the rights conferred by, and subject to all the restrictions imposed by, this Agreement, and as a condition to such transfer, each such
transferee shall execute and deliver an Instrument of Accession in the form of Schedule II agreeing to be bound by the provisions of this Agreement. 
  

	 	5.	Election of Directors. 


(a) Board Designation Rights; Initial Members. Each Stockholder hereby agrees to vote all of the Stock of the Company now owned or
hereafter acquired by such party (and attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions (including, but not limited, to the nomination of specified persons, the
execution of written consents and the calling of a stockholder meeting for the purpose of electing such specified persons) to cause and maintain the election to the Board of Directors of the Company, to the extent permitted pursuant to the
Company’s Amended and Restated Certificate of Incorporation, as amended from time to time (the “Certificate of Incorporation”), the following: 

  
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 (i) the then current Chief Executive Officer of the Company as one (1) of the Common
Directors (as defined in the Certificate of Incorporation), who shall initially be Daniel Stephen Hafner; 
 (ii) one
(1) person designated by the holders of a majority of the outstanding shares of Common Stock, voting as a separate class, as the other Common Director, who shall initially be Paul English; 

(iii) two (2) persons designated by the holders of at least seventy percent (70%) of the outstanding shares of the Series A
Preferred Stock, voting as a separate class on an as-converted to Common Stock basis (the “Series A Designators”), as the two Series A Directors (as defined in the Certificate of Incorporation), who shall initially be Joel
Cutler and Terrell Jones; 
 (iv) one (1) person designated by the holders of at least a majority of the outstanding shares
of the Series C Stock, voting as a separate class (the “Series C Designators”), as the Series C Director (as defined in the Certificate of Incorporation), who shall initially be Hendrik Nelis; 

(v) for so long as Sequoia Capital Growth Fund III or one or more of its affiliates (as defined in Rule 501 of Regulation D under the
Securities Act of 1933, as amended) (“Sequoia”) holds at least 1,000,000 shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar
event affecting the Preferred Stock), one (1) person designated by Sequoia as the Series D Director (as defined in the Certificate of Incorporation), who shall initially be Michael Moritz. In the event Sequoia does not hold at least 1,000,000
shares of the Company’s Preferred Stock (as adjusted from time to time to reflect any stock split, stock dividend, reverse stock split or similar event affecting the Preferred Stock), then, in lieu of Sequoia, the holders of at least a majority
of the outstanding shares of the Series D Stock, voting as a separate class, shall be entitled to designate one (1) person as the Series D Director. The individual, entity, or group of individuals and/or entities who has the right to designate
the Series D Director pursuant this Section 5(a)(v) shall be referred to herein as the “Series D Designator”; 
 (vi) one (1) person designated jointly by the Series A Designators, the Series C Designators and the Series D Designator, each voting as a separate series, as the Preferred and Common Director (as
defined in the Certificate of Incorporation), who shall initially be Gregory Stanger; and 
 (v) one (1) person designated
jointly by the Series A Designators, the Series C Designators, and the Series D Designator, each voting as a separate series, as the Remaining Director (as defined in the Certificate of Incorporation), who shall initially be Brian Sharples.


  
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 For the purposes of this Agreement, (x) “Stock” shall mean and include all
Convertible Preferred Stock and all shares of Common Stock, and all other securities of the Company which may be exchangeable for, convertible into or issued in exchange for or in respect of shares of Common Stock (whether by way of stock split,
stock dividends, combination, reclassification, reorganization or any other means), (y) “Board Designee” shall mean any individual who is designated for election to the Company’s Board of Directors pursuant to this
Section 5; and (z) “Designator” or “Designators” shall mean, as applicable, any individual, entity, or group of individuals and/or entities who has the right to designate one (1) or more Board Designees for
election to the Company’s Board of Directors pursuant to this Section 5. 
 (b) Removal; Successor Directors.
In the absence of any designation from the appropriate Designator or Designators, the Board Designee previously designated by them and then serving shall be reelected if still eligible to serve as provided herein. From time to time during the term
of this Agreement, a Designator or Designators may, in their sole discretion: 
 (i) elect to initiate the removal from the
Company’s Board of Directors of any incumbent Board Designee who occupies a board seat for which such Designator or Designators are entitled to designate the Board Designee under Section 5(a), and/or 

(ii) designate a new Board Designee for election to a board seat for which such Designator or Designators are entitled to designate the
Board Designee under Section 5(a) (whether to replace a prior Board Designee or to fill a vacancy in such board seat); provided, however, that any new Board Designee designated by the Series A Designators, the Series C Designators and
the Series D Designator for the Preferred and Common Director must be ratified by the holders of a majority of the outstanding shares of Common Stock, which ratification may not be unreasonably withheld or delayed; provided further, however,
no such ratification is required for any new Board Designee who has general experience with marketing and the travel related e-commerce industry. 
 In the event of an initiation of removal of a Board Designee pursuant to Section 5(b)(i), the Stockholders shall vote all of the Stock of the Company now owned or hereafter acquired by them (and
attend, in person or by proxy, all meetings of stockholders called for the purpose of electing directors), and agree to take all actions to cause the removal from the Company’s Board of Directors of the Board Designee or Designees so designated
for removal by the appropriate Designator or Designators; provided, however, in no event shall any party vote to remove any Board Designee unless the appropriate Designator or Designators have so directed pursuant to Section 5(b)(i). In
the event of designation of a Board Designee pursuant to Section 5(b)(ii), the parties shall vote all of the Stock of the Company now owned or hereafter acquired by them (and attend, in person or by proxy, all meetings of stockholders called
for the purpose of electing directors), and agree to take all actions to cause the election to the Company’s Board of Directors of any new Board Designee or Designees so designated for election to the Company’s Board of Directors pursuant
to Section 5(b)(ii). 
 Without the consent of the Requisite Investors, the parties hereby agree that they will not take
any action, by vote or otherwise, to increase the authorized number of directors constituting the Company’s Board of Directors to more than eight (8) directors, unless the holders of


  
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Convertible Preferred Stock are then entitled to elect, in addition to the two (2) Series A Directors described in Section 5(a)(iii) above and one Series C Director described in
Section 5(a)(iv) above, two additional Series A Directors and one additional Series C Director pursuant to Article 4B, subparagraph 6C of the Certificate of Incorporation (the “Additional Directors”), in which case the
Company’s Board of Directors shall consist of no more than eleven (11) members. If and for so long as the holders of Convertible Preferred Stock are entitled to elect the Additional Directors pursuant to Article 4B, subparagraph 6C of the
Certificate of Incorporation, each of the parties hereto hereby agrees to vote all of the Stock of the Company now owned or hereafter acquired in favor of the election to the Board of Directors of two (2) persons designated from time to time by
the Series A Designators and one (1) person designated from time to time by the Series C Designators. 
 (c) Observer
Rights. Oak Investment Partners XII, Limited Partnership shall be entitled to have a representative (the “Oak Board Observer”) attend all meetings of the Company’s Board of Directors and all committees thereof in a
nonvoting capacity (subject to the Company’s determination upon the advice of counsel that the Oak Board Observer’s presence may violate attorney-client privilege or would otherwise be excused from a meeting were the Oak Board Observer a
director) and, in this respect, the Company shall give the Oak Board Observer copies of all notices, minutes, consents and other materials that it provides to its directors. The Oak Board Observer may participate in discussions of matters brought to
the Company’s Board of Directors. As a condition to attending such meetings and receiving such materials, the Oak Board Observer will agree in writing to hold in confidence and trust and not use or disclose any confidential information provided
to or learned by it in connection with its rights under this paragraph as if the Oak Board Observer were a member of the Company’s Board of Directors. 
 6. Drag-Along Rights. If (a) a majority of the members of the Company’s Board of Directors and (b) the Requisite Investors approve a sale of Company or all or substantially all of
Company’s assets, whether by means of a merger, consolidation, sale of stock or assets or otherwise (a “Sale of the Company”), all Investors and Holders shall consent to and vote their Shares in favor of the Sale of the
Company, and if the Sale of the Company is structured as (i) a merger or consolidation of the Company, or a sale of all or substantially all of the Company’s assets, each Investor and Holder shall waive any dissenters’ rights,
appraisal rights or similar rights in connection with such merger, consolidation or asset sale, or (ii) a sale of the stock of the Company, the Investors and Holders shall agree to sell their Shares on the terms and conditions approved by
(x) a majority of the members of the Company’s Board of Directors and (y) the Requisite Investors; provided, however, that, (A) all proceeds from such Sale of the Company shall be payable to the holders of the
Company’s Stock in accordance with the Certificate of Incorporation, including, without limitation, Article 4B, Paragraph 3 thereof, which entitles the holders of Convertible Preferred Stock to a liquidation preference payment and other rights
set forth therein, except that, at the discretion of the Company’s Board of Directors, holders of shares of Common Stock that are unvested on the date that the Sale of the Company is consummated may receive, in lieu of proceeds from the Sale of
the Company and in exchange for their unvested shares of Common Stock, unvested securities or options to acquire securities of the entity surviving the Sale of the Company on an equitable basis, (B) except as set forth in the preceding clause
(A), the terms of such Sale of the Company applicable to holders of shares 

  
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of each series of Convertible Preferred Stock, in their capacities as holders thereof, shall be no less favorable than the terms applicable to the holders of all other series of Convertible
Preferred Stock in their capacities as holders thereof and (C) if the Requisite Investors are given the option to choose the form of consideration to be received in such Sale of the Company on its Stock, the obligations of a Holder or other
Investor to approve the Sale of the Company under this Section 6 shall be conditioned upon it having received the same option. Each Holder and Investor hereby irrevocably constitutes and appoints the Company and any representative or agent
thereof, with full power of substitution, as its true and lawful attorney-in-fact with full irrevocable power and authority in the place and stead of such Holder or Investor and in the name of such Holder or Investor or in its own name, for the
purpose of carrying out the terms of this Section 6, to take any and all appropriate action and to execute any and all documents and instruments which may be necessary or desirable to accomplish the purposes of this Section 6. Such Holder
and Investor hereby ratifies all that said attorneys shall lawfully do or cause to be done by virtue hereof. 
 7.
Termination. This Agreement, and the respective rights and obligations of the parties hereto, shall terminate upon the completion of a firm commitment underwritten public offering of Common Stock in which (a) the aggregate gross proceeds
received by the Company shall be at least $25,000,000, and (b) the per share price paid by the public for such shares shall be at least $31.09 (appropriately adjusted to reflect any subdivision or combination of the Common Stock occurring after
the date hereof) (a “Qualified Public Offering”); provided, however, that Sections 1 through 3 shall terminate on the earlier of (i) the completion of a Qualified Public Offering and (ii) ten (10) years
after the date hereof. 
 8. Notices. Any notices or other communication required to be sent or given hereunder by any of
the parties shall in every case be in writing and shall be deemed properly served if (a) delivered personally, (b) sent by certified U.S. Mail, with first class postage prepaid, return receipt requested, (c) delivered by a recognized
overnight courier service, with certification of receipt requested, or (d) sent by facsimile transmission with a confirmation copy sent by overnight courier, in each case, to the parties at the addresses and telecopy numbers as set forth below
or at such other addresses or telecopy number as may be furnished in writing by any party pursuant to this Section 8 (except that notices of changes of address or a telecopy number shall only be effective upon receipt): 

if to the Company or any other party hereto that is also a party to the Purchase Agreement, at the address of such party set forth in the
Purchase Agreement, with a copy sent to such party’s legal counsel designated in the Purchase Agreement, if applicable; 

if to any other party hereto as of the date of the Agreement, to such party at its address set forth on Schedule I hereto;

 if to a Holder who subsequently becomes a party to this Agreement, at its address set forth on the Instrument of Accession
pursuant to which such Holder became a party to this Agreement; and 

  
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 if to an Investor who subsequently becomes a party to this Agreement, at its address set
forth on the Instrument of Accession pursuant to which such Investor became a party to this Agreement. 
 Date of service of such notice shall
be (w) the date such notice is personally delivered, (x) three (3) days after the date of mailing if sent by certified mail, (y) two (2) days after date of delivery to the overnight courier if sent by overnight courier (as
evidenced by a written receipt from the courier), or (z) the next succeeding business day after transmission by facsimile. 

9. Failure to Deliver Shares. If a Holder becomes obligated to sell any Shares owned by, or held for the benefit of, such Holder
to an Investor or a Qualified Transferee under this Agreement and fails to deliver such Shares in accordance with the terms of this Agreement, such Investor may, at its option, in addition to all other remedies it may have, send to the Company for
the benefit of such Holder the purchase price for such Shares as is herein specified. Thereupon, the Company upon written notice to said Holder, (a) shall cancel on its books the certificate(s) representing the Shares to be sold and
(b) shall issue, in lieu thereof, in the name of such Investor, a new certificate(s) representing such Shares, and thereupon all of said Holder’s rights in and to such shares shall terminate. The Company may exercise a similar remedy in
enforcing its rights under Section 2. If a Holder transfers any Shares to a Purchaser in violation of this Agreement, the Company may, at the election of a majority of the disinterested members of the Company’s Board of Directors, cancel
on the books of the Company any shares of capital stock then held by such Holder, and any such breaching Holder agrees to purchase from the Purchasers and any transferee a number of shares of capital stock equal to the amount so transferred in
violation of this Agreement. 
 10. Specific Performance; Proxy. The rights of the parties under this Agreement are
unique and, accordingly, the parties shall, in addition to such other remedies as may be available to any of them at law or in equity, have the right to enforce their rights hereunder by actions for specific performance to the extent permitted by
law. The voting of shares of capital stock pursuant to this Agreement may be effected in person, by proxy, by written consent or in any other manner permitted by applicable law. Each Stockholder hereby grants to the Secretary of the Company, in the
event that such Stockholder fails to vote its shares of capital stock as required by this Agreement, a proxy coupled with an interest in all shares of capital stock owned by such Stockholder empowering the Secretary to vote such shares as to such
matters as are set forth in Section 5 hereof, which proxy is irrevocable until this Agreement terminates pursuant to its terms or this Section 10 is amended to remove such grant of proxy in accordance with Section 14 of this
Agreement. 
 11. Legend. The certificates representing the Shares shall bear on their face a legend indicating the
existence of the restrictions imposed hereby. 
 12. Entire Agreement. This Agreement, the Founder Stock Agreements and
the Purchase Agreement (including any and all exhibits, schedules and other instruments contemplated thereby) constitute the entire agreement among the parties with respect to the subject matter hereof and supersede all prior agreements or
understandings between them or any of them as to such subject matter. 

  
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 13. Waivers and Further Agreements. Except as provided in Section 14, any of the
provisions of this Agreement may be waived by an instrument in writing executed and delivered by Requisite Investors. Any waiver by any party of a breach of any provision of this Agreement shall not operate or be construed as a waiver of any
subsequent breach of that provision or of any other provision hereof. Each of the parties hereto agrees to execute all such further instruments and documents and to take all such further action as any other party may reasonably require in order to
effectuate the terms and purposes of this Agreement. Notwithstanding the foregoing, no waiver may treat one Investor more adversely than any other Investor without the consent of such Investor adversely affected by such waiver. 

14 Amendments. Except as otherwise expressly provided herein, this Agreement may not be amended except by an instrument in writing
executed by (i) the Company and (ii) the Requisite Investors. Notwithstanding the foregoing, (i) the consent of the Holders holding a majority of the outstanding shares of Common Stock subject to this Agreement shall be required for
any amendment that materially adversely affects the rights of the Holders, (ii) no amendment may treat one Investor more adversely than any other Investor without the consent of such Investor adversely affected by such amendment, (iii) no
amendment may treat one Holder more adversely than any other Holder without the consent of such Holder, and (iv) no amendment, waiver or modification to the rights of a Designator to appoint or remove a Board Designee pursuant to Section 5
shall be effective without the consent of such Designator. 
 15. Assignment; Successors and Assigns. This Agreement
shall be binding upon and shall inure to the benefit of the parties hereto and their respective heirs, executors, legal representatives, successors and permitted transferees, except as may be expressly provided otherwise herein. 

16. Severability. In case any one or more of the provisions contained in this Agreement shall for any reason be held to be
invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect any other provision of this Agreement and such invalid, illegal and unenforceable provision shall be reformed and construed so that it
will be valid, legal, and enforceable to the maximum extent permitted by law. 
 17. Counterparts. This Agreement may be
executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. 
 18. Section Headings. The headings contained in this Agreement are for reference purposes only and shall not in any way affect the meaning or interpretation of this Agreement. 

19. Governing Law. This Agreement shall be construed and enforced in accordance with and governed by the laws of the General
Corporation Law of the State of Delaware as to matters within the scope thereof, and as to all other matters shall be governed by and construed in accordance with the internal laws of the Commonwealth of Massachusetts, without regard to its
principles of conflicts of laws. 

  
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 20. Additional Parties. Any purchaser of Convertible Preferred Stock shall become a
party to this Agreement by executing and delivering to the Company an executed Instrument of Accession in the form of Schedule II hereto. Upon such execution and delivery, such purchaser shall be deemed to be an “Investor” hereunder
with all of the rights and obligations thereof. Unless otherwise consented to by the Board of Directors, the Company shall cause each officer, director, employee, consultant or other service provider of the Company who acquires shares of Common
Stock representing greater than 1% of the fully-diluted capital stock of the Company or options to purchase such number of shares of Common Stock, to become a party to this agreement by executing and delivering to the Company an executed Instrument
of Accession in the form of Schedule II hereto. Upon such execution and delivery, such holder shall be deemed to be a “Holder” hereunder with all of the rights and obligations thereof. 

[signature pages follow] 

  
 Page 11 of 41









 IN WITNESS WHEREOF, the undersigned have executed this Sixth Amended and Restated Stock
Restriction and Co-Sale Agreement as a sealed instrument as of the day and year first above written. 
 COMPANY: 

 

			
	KAYAK SOFTWARE CORPORATION
		
	By:	 	/s/ Steve Hafner        
	Name:	 	Steve Hafner
	Title:	 	CEO

 [The remainder of this page is intentionally left blank.] 

  
 Signature Page
to Sixth A&R Co-Sale Agreement 









	
	HOLDERS:
	
	/s/ Daniel Stephen Hafner
	Daniel Stephen Hafner

  

	
	
	/s/ Paul English
	Paul English

  

			
	McKane 2007 Grandchildren Trust
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	Title:	 	

  

			
	J.M. Hafner Trust
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	Title:	 	

  

			
	Joseph A. Hafner Trust
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	Title:	 	

  

			
	Merrill T. Hafner Trust
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	Title:	 	

  

			
	D.S. Hafner Trust
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	Title:	 	


  
 Signature Page
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	Hafner Investment Partnership
		
	By:	 	/s/ Daniel Stephen Hafner
	Name:	 	
	 Title:
	 	

  

			
	The Paul M. English 2007 Irrevocable Family Trust
		
	By:	 	/s/ Paul M. English
	Name:	 	Paul M. English, Trustee

  

			
		
	By:	 	 
	Name:	 	Jean A. English, Trustee

  

			
	The Paul M. English 2006 Irrevocable Family Trust
		
	By:	 	/s/ Paul M. English
	Name:	 	Paul M. English, Trustee

  

			
		
	By:	 	 
	Name:	 	Jean A. English, Trustee

  

	
	
	  
	 Andrew Patterson


  

	
	
	  
	 Alexander Morcos


  

	
	
	  
	 Benjamin P. Davenport


  

	
	
	  
	 John E. Crandon III


  

	
	
	  
	 Jean A. English



  
 Signature Page
to Sixth A&R Co-Sale Agreement 









	
	 
	Anastasios Makris
	
	 
	Melissa Fredette
	
	 
	Jonathan Spewak
	
	The Paul M. English 2009 Charitable Remainder Unitrust I


 

			
		
	By:	 	/s/ Paul M. English
	Name: Paul M. English, Trustee

  

			
		
	By:	 	 
	Name: Jean A. English, Trustee
	
	The Paul M. English 2009 Charitable Remainder Unitrust II

  

			
		
	By:	 	/s/ Paul M. English
	Name: Paul M. English, Trustee

  

			
		
	By:	 	 
	Name: Jean A. English, Trustee
	
	 
	John Bullock
	
	 
	Shehzad Daredia


  
 Signature Page
to Sixth A&R Co-Sale Agreement 








 INVESTORS: 
  

									
	GENERAL CATALYST GROUP II, L.P.	 		 	GENERAL CATALYST GROUP III, L.P.
			
	 By: General Catalyst Partners II, L.P.
 Its General Partner
	 		 	 By: General Catalyst Partners III, L.P.
 Its General Partner

			
	 By: General Catalyst GP II, LLC
 Its General Partner
	 		 	 By: General Catalyst GP III, LLC
 Its General Partner

					
	By:	 	/s/ William J. Fitzgerald	 		 	By:	 	/s/ William J. Fitzgerald
	Name: William J. Fitzgerald	 		 	Name: William J. Fitzgerald
	Title: Member and Chief Financial Officer	 		 	Title: Member and Chief Financial Officer
			
	GC ENTREPRENEURS FUND II, L.P.	 		 	GC ENTREPRENEURS FUND III, L.P.
			
	 By: General Catalyst Partners II, L.P.
 Its General Partner
	 		 	 By: General Catalyst Partners III, L.P.
 Its General Partner

			
	 By: General Catalyst GP II, LLC
 Its General Partner
	 		 	 By: General Catalyst GP III, LLC
 Its General Partner

					
	By:	 	/s/ William J. Fitzgerald	 		 	By:	 	/s/ William J. Fitzgerald
	Name: William J. Fitzgerald	 		 	Name: William J. Fitzgerald
	Title: Member and Chief Financial Officer	 		 	Title: Member and Chief Financial Officer
			
	GENERAL CATALYST GROUP V, L.P.	 		 	GC ENTREPRENEURS FUND V, L.P.
			
	 By: General Catalyst Partners V, L.P.
 Its General Partner
	 		 	 By: General Catalyst Partners V, L.P.
 Its General Partner

			
	 By: General Catalyst GP V, LLC
 Its General Partner
	 		 	 By: General Catalyst GP V, LLC
 Its General Partner

					
	By:	 	/s/ William J. Fitzgerald	 		 	By:	 	/s/ William J. Fitzgerald
	Name: William J. Fitzgerald	 		 	Name: William J. Fitzgerald
	Title: Member and Chief Financial Officer	 		 	Title: Member and Chief Financial Officer


  
 Signature Page
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	 GENERAL CATALYST GROUP V
 SUPPLEMENTAL, L.P.

		
	By:	 	General Catalyst Partners V, L.P.
	Its General Partner
		
	By:	 	General Catalyst GP V, LLC
	Its General Partner
		
	By:	 	/s/ William J. Fitzgerald
	 Name: William J. Fitzgerald

	 Title: Member and Chief Financial Officer



  
 Signature Page
to Sixth A&R Co-Sale Agreement 









	
	
	/s/ Daniel Stephen Hafner
	Daniel Stephen Hafner


  
 Signature Page
to Sixth A&R Co-Sale Agreement 









	
	
	/s/ Paul English
	Paul English


  
 Signature Page
to Sixth A&R Co-Sale Agreement 









					
	 ACCEL LONDON II L.P.

		
	 By:
	 	Accel London II Associates L.P.
	 Its:
	 	General Partner
		
	 By:
	 	Accel London II Associates L.L.C.
	 Its:
	 	General Partner
		
	 By:
	 	/s/ Jonathan Biggs
		 	Name:	 	Jonathan Biggs
		 	Title:	 	Attorney in Fact

  

					
	 ACCEL LONDON INVESTORS 2006 L.P.

		
	 By:
	 	Accel London II Associates L.L.C.
	 Its:
	 	General Partner
		
	 By:
	 	/s/ Jonathan Biggs
		 	Name:	 	Jonathan Biggs
		 	Title:	 	Attorney in Fact


  
 Signature Page
to Sixth A&R Co-Sale Agreement 









			
	 SEQUOIA CAPITAL XI

SEQUOIA TECHNOLOGY PARTNERS XI

SEQUOIA CAPITAL XI PRINCIPALS

FUND

	
	 By: SC XI Management, LLC

A Delaware Limited Liability Company

General Partner of Each



			
		
	By:	 	/s/ Michael Moritz
	Name:	 	
	Title:	 	Managing Member

  

			
	 SEQUOIA CAPITAL GROWTH FUND III

SEQUOIA CAPITAL GROWTH PARTNERS III

SEQUOIA CAPITAL GROWTH III PRINCIPALS FUND

		
	By:	 	 SCGF III Management, LLC
 A Delaware Limited Liability Company
 General Partner of
Each



			
		
	By:	 	/s/ Michael Moritz
	Name:	 	
	Title:	 	Managing Member


  
 Signature Page
to Sixth A&R Co-Sale Agreement 








 SCHEDULE I 

KAYAK SOFTWARE CORPORATION  
 SCHEDULE OF HOLDERS AND INVESTORS 
 Investors: 

General Catalyst Group II, L.P. 
 GC
Entrepreneurs Fund II, L.P. 
 General Catalyst Group III, L.P. 
 GC Entrepreneurs Fund III, L.P. 
 General Catalyst Group V, L.P. 

General Catalyst Group V Supplemental, L.P. 
 GC
Entrepreneurs Fund V, L.P. 
 20 University Road, Suite 450 
 Cambridge, MA 02138 
 Fax: (617) 234-7040 
 Attn: Joel Cutler 
 Daniel Stephen Hafner 
 33 North Water Street, Apartment 610, 
 South Norwalk, CT 06854 

Fax: (203) 899-3125 
 Paul English

 204 Pleasant Street 
 Arlington, MA
02476 
 Greg Slyngstad 
 1736 W.
Beaver Lake Drive SE 
 Sammamish, WA 98075 
 Sequoia Capital Growth Fund III 
 Sequoia Capital Growth Partners III 

Sequoia Capital Growth III Principals Fund 

Sequoia Capital XI 
 Sequoia Technology Partners
XI 
 Sequoia Capital XI Principals Fund 

3000 Sand Hill Road 
 Bldg 4, Suite 250

 Menlo Park, CA 94025 







 Accel London II, L.P. 
 Accel London Investors 2006 L.P. 
 428 University Avenue 

Palo Alto, CA 94301-1812 
 Fax:
(650) 614-4880 
 Attn: Richard Zamboldi 
 Notices also sent to 
 16 St. James’s Street 

London SW1A 1ER 
 United Kingdom 

Fax: +44 (0) 20 7170 1099 
 Attn: Jonathan Biggs

 Attn: Harry Nelis 
 Norwest Venture
Partners VII-A LP 
 Norwest Venture Partners X, LP 
 525 University Avenue, Suite 800 
 Palo Alto, CA 94301 

650.321.8000 
 Oak Investment Partners XII,
Limited Partnership 
 One Gorham Island 

Westport, CT 06880 
 Tenaya Capital V, L.P.

 Tenaya Capital V V-P, L.P. 
 Tenaya
Capital B, LP 
 2965 Woodside Road, Suite A 
 Woodside, CA 94062 
 Trident Capital Fund-V, L.P 

Trident Capital Fund-V Affiliates Fund, L.P. 

Trident Capital Fund-V Affiliates Fund (Q), L.P. 

Trident Capital Fund-V Principals Fund, L.P. 

Trident Capital Parallel Fund-V, C.V. 
 505
Hamilton Ave, Suite 200 
 Palo Alto, CA 94301 







 Gold Hill Venture Lending 03, L.P. 
 Two Newton Executive Park, Suite 203 
 Newton, MA 02462 

The English Family 2010 Trust 
 51 Winchester
Road 
 Arlington, MA 02474 







 Holders: 
 Daniel Stephen Hafner 
 33 North Water Street, Apartment 610, 

South Norwalk, CT 06854 
 Fax:
(203) 899-3125 
 Paul English 

204 Pleasant Street 
 Arlington, MA 02476

 McKane 2007 Grandchildren Trust 
 48
Owenoke Park 
 Westport, CT 06880 

J.M. Hafner Trust 
 6 Longfellow Lane

 Houston, TX 77005 
 Joseph A. Hafner
Trust 
 1316 Pequot Avenue 
 Southport,
CT 06890 
 Merrill T. Hafner Trust 

1316 Pequot Avenue 
 Southport, CT 06890

 Paul M. English and Jean A English, as trustees of The Paul M. English 2007 Irrevocable Family Trust 

204 Pleasant Street 
 Arlington, MA 02476

 Paul M. English and Jean A English, as trustees of The Paul M. English 2006 Irrevocable Family Trust 

204 Pleasant Street 
 Arlington, MA 02476

 D.S. Hafner Trust 
 1316 Pequot
Avenue 
 Southport, CT 06890 
 Hafner
Investment Partnership 
 23 Farnham Park Drive 
 Houston, TX 77024 
 Andrew Patterson 
 50 Murray Street, #1116 
 New York, NY 10007 







 Alexander Morcos 
 310 E 9th
Street, #1 
 New York, NY 10001 

Benjamin P. Davenport 
 229 Chrystie Street,
#813 
 New York, NY 10002 
 John E.
Crandon III 
 36 Grattan Street 
 San
Francisco, CA 94117 
 Anastasios P. Makris 
 24 18th Street 
 Lowell, MA 01850 
 Jean A. English 
 51 Winchester Road 
 Arlington, MA 02474 
 The Paul M. English 2009 Charitable Remainder Unitrust I 

204 Pleasant Street 
 Arlington, MA 02476

 The Paul M. English 2009 Charitable Remainder Unitrust II 
 204 Pleasant Street 
 Arlington, MA 02476 
 Jonathan Spewak 
 1085 Commonwealth Ave. #300 

Boston, MA 02215 
 Melissa Fredette 

224 Stevens Street 
 Marlboro, MA 01752

 John Bullock 
 1 Fawn Circle

 Bedford, MA 01730 
 Shehzad Daredia

 295 Park Avenue South 
 Apt. 160

 New York, NY 10010 







 Kellie Macdonald 
 5 Green Lane 
 Unit B 
 Greenwich, CT 06831 
 Stephen Squadrito 
 31 Carp Road 
 Milford, MA 01757 
 Nilesh Thakker 
 18892 Woodleigh Court 
 Saratoga, CA 95070 
 Windspeed Ventures III, LP 

52 Waltham Street 
 Lexington, MA 02421

 Evergreen Opportunity Fund LLC 

1117 Sawgrass Corporate Parkway 
 Sunrise, FL
33323 
 Keith D. Melnick 
 77 Mill
Hill Road 
 Southport, CT 06890 

Institutional Venture Partners XII, L.P. 
 3000
Sand Hill Road 
 Building 2, Suite 250 

Menlo Park, CA 94025 
 Sprout Opportunity Fund
I, LLC 
 1117 Sawgrass Corporate Parkway 
 Sunrise, FL 33323 
 Sprout Opportunity Fund III, LLC 

1117 Sawgrass Corporate Parkway 
 Sunrise, FL
33323 
 John Bullock & Laura Bullock JT TEN 
 1 Fawn Circle 
 Bedford, MA 01730 
 Leah Rounds 
 108 Hickory Woods Lane 
 Stratford, CT 06614 







 James Giza 
 15 Pierce Road 
 Sutton, MA 01590 
 Robert M. Birge 
 46 Lyons Plain Road 
 Weston, CT 06883 
 Rose O’Donnell 
 8 Sassafras Road 
 Westford, MA 01886 
 Mark S. Dionne 
 199 Jackson Street 
 Newton, MA 02459 







 SCHEDULE II 
 KAYAK SOFTWARE CORPORATION 
 INSTRUMENT OF ACCESSION 

The
undersigned,                                , as a condition precedent to becoming
the owner or holder of record
of                                    
(             ) shares of the                      stock, par value $.001
per share, of KAYAK Software Corporation, a Delaware corporation (the “Company”), or options to purchase such stock, hereby agrees to become a [Holder/Investor] under that certain Fifth Amended and Restated Stock
Restriction and Co-Sale Agreement dated as of December         , 2007 by and among the Company and other stockholders of the Company party thereto. This Instrument of Accession shall take effect and
shall become an integral part of, and the undersigned shall become a party to and bound by, said Fifth Amended and Restated Stock Restriction and Co-Sale Agreement immediately upon execution and delivery to the Company of this Instrument of
Accession. 
 IN WITNESS WHEREOF, this INSTRUMENT OF ACCESSION has been duly executed by or on behalf of the undersigned, as of
the date below written. 
  

			
	Signature:
	
	 
	(Print Name)	 	 
		
	Address:	 	
		
	 	 	 
		
	 	 	 


  

			
	Date:	 	 


  

			
	Accepted:	 	
		 	


  

			
	KAYAK SOFTWARE CORPORATION
		
	By:	 	 
		 	Name:
		 	Title:


  

			
	Date: