Table of Contents 6.
Indebtedness (Continued) The Term Loan Facility matures on December 17, 2010 and amortizes quarterly at a rate of $1 million.
Principal amounts repaid under the Term Loan Facility may not be re-borrowed.
The Credit Facility is secured by certain aircraft.
The Credit Facility includes a covenant that requires periodic appraisal of the aircraft at current market value and requires American to pledge more aircraft or cash collateral if the loan amount is more than 50 percent of the appraised value (after giving effect to sublimits for specified categories of aircraft).
In addition, the Credit Facility is secured by all of American’s existing route authorities between the United States and Tokyo, Japan, together with certain slots, gates and facilities that support the operation of such routes.
American’s obligations under the Credit Facility are guaranteed by AMR, and AMR’s guaranty is secured by a pledge of all the outstanding shares of common stock of American.
The Credit Facility contains a covenant (the Liquidity Covenant) requiring American to maintain, as defined, unrestricted cash, unencumbered short term investments and amounts available for drawing under committed revolving credit facilities which have a final maturity of at least 12 months after the date of determination, of not less than $1.25 billion for each quarterly period through the remaining life of the Credit Facility.
In addition, the Credit Facility contains a covenant (the EBITDAR Covenant) requiring AMR to maintain a ratio of cash flow (defined as consolidated net income, before interest expense (less capitalized interest), income taxes, depreciation and amortization and rentals, adjusted for certain gains or losses and non-cash items) to fixed charges (comprising interest expense (less capitalized interest) and rentals) of at least the amount specified below for each period of four consecutive quarters ending on the dates set forth below:
## Table 0 ##
AMR and American were in compliance with the Liquidity Covenant and the EBITDAR Covenant at December 31, 2006 and expect to be able to comply with these covenants.
However, given fuel prices that are high by historical standards and the volatility of fuel prices and revenues, it is difficult to assess whether AMR and American will, in fact, be able to continue to comply with the Liquidity Covenant and, in particular, the EBITDAR Covenant, and there are no assurances that they will be able to do so.
Failure to comply with these covenants would result in a default under the Credit Facility which — - if the Company did not take steps to obtain a waiver of, or otherwise mitigate, the default — - could result in a default under a significant amount of the Company’s other debt and lease obligations and have a material adverse impact on the Company.
In September 2005, American sold and leased back 89 spare engines with a book value of $105 million to a variable interest entity (VIE).
The net proceeds received from third parties were $133 million.
American is considered the primary beneficiary of the activities of the VIE as American has substantially all of the residual value risk associated with the transaction.
As such, American is required to consolidate the VIE in its financial statements.
At December 31, 2006, the book value of the engines was $94 million and was included in Flight equipment on the consolidated balance sheet.
The engines serve as collateral for the VIE’s long-term debt of $123 million at December 31, 2006, which has also been included in the consolidated balance sheet.
The VIE has no other significant operations.
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS OF AMERICAN AIRLINES GROUP INC.  2012, substantially all of our defined benefit pension plans were frozen and we began providing enhanced benefits under our defined contribution pension plans for certain groups.
We use a December 31 measurement date for all of our defined benefit pension plans.
We also provide certain retiree medical and other postretirement benefits, including health care and life insurance benefits, to retired employees.
Effective November 1, 2012, we modified our retiree medical and other postretirement benefits plans to eliminate the company subsidy for employees who retire on or after November 1, 2012.
As a result of modifications to our retiree medical and other postretirement benefits plans in 2012, we recognized a negative plan amendment of $1.9 billion, which is included as a component of actuarial gain in OCI and will be amortized over the future service life of the active plan participants for whom the benefit was eliminated, or approximately eight years.
As of December 31, 2016, $871 million of actuarial gain remains to be amortized.
Benefit Obligations, Fair Value of Plan Assets and Funded Status The following tables provide a reconciliation of the changes in the pension and retiree medical and other postretirement benefits obligations, fair value of plan assets and a statement of funded status as of December 31, 2016 and 2015:
## Table 1 ##
The December 31, 2016 and 2015 pension actuarial (gain) loss primarily relates to weighted average discount rate assumption changes and changes to our mortality assumptions.
The December 31, 2016 and 2015 retiree medical and other postretirement benefits actuarial gain primarily relates to medical trend and cost assumption changes, favorable plan experience adjustments and weighted average discount rate assumption changes.
At December 31, 2015, certain trust assets totaling approximately $24 million, were added to the retiree medical and other postretirement benefits plans asset values that were previously offset against the benefit obligation.
Table of Contents configuration, amenities provided to passengers, loyalty programs, the automation of travel agent reservation systems, onboard products, markets served and other services.
We compete with both major network airlines and low-cost carriers throughout our network.
International In addition to our extensive domestic service, we provide international service to Canada, Central and South America, Asia, Europe, Australia and New Zealand.
In providing international air transportation, we compete with U. S.  airlines, foreign investor-owned airlines and foreign state- owned or state-affiliated airlines, including carriers based in the Middle East, the three largest of which we believe benefit from significant government subsidies.
In order to increase our ability to compete for international air transportation service, which is subject to extensive government regulation, U. S.  and foreign carriers have entered into marketing relationships, alliances, cooperation agreements and JBAs to exchange traffic between each other’s flights and route networks.
See “Ticket Distribution and Marketing Agreements” above for further discussion.
Employees and Labor Relations The airline business is labor intensive.
In 2016, mainline and regional salaries, wages and benefits were our largest expense and represented approximately 35% of our total operating expenses.
Labor relations in the air transportation industry are regulated under the Railway Labor Act (RLA), which vests in the National Mediation Board (NMB) certain functions with respect to disputes between airlines and labor unions relating to union representation and collective bargaining agreements (CBAs).
When an RLA CBA becomes amendable, if either party to the agreement wishes to modify its terms, it must notify the other party in the manner prescribed under the RLA and as agreed by the parties.
Under the RLA, the parties must meet for direct negotiations, and, if no agreement is reached, either party may request the NMB to appoint a federal mediator.
The RLA prescribes no set timetable for the direct negotiation and mediation process.
It is not unusual for those processes to last for many months and even for several years.
If no agreement is reached in mediation, the NMB in its discretion may declare under the RLA at some time that an impasse exists, and if an impasse is declared, the NMB proffers binding arbitration to the parties.
Either party may decline to submit to binding arbitration.
If arbitration is rejected by either party, an initial 30-day “cooling off” period commences.
Following the conclusion of that 30-day “cooling off” period, if no agreement has been reached, “self-help” (as described below) can begin unless a Presidential Emergency Board (PEB) is established.
A PEB examines the parties’ positions and recommends a solution.
The PEB process lasts for 30 days and (if no resolution is reached) is followed by another “cooling off” period of 30 days.
At the end of a “cooling off” period (unless an agreement is reached, a PEB is established or action is taken by Congress), the labor organization may exercise “self-help,” such as a strike, and the airline may resort to its own “self-help,” including the imposition of any or all of its proposed amendments to the CBA and the hiring of new employees to replace any striking workers.
The table below presents our approximate number of active full-time equivalent employees as of December 31, 2016.
## Table 2 ##

<table><tr><td>Four Quarter Period Ending</td><td>Cash Flow Coverage Ratio</td></tr><tr><td>March 31, 2007</td><td>1.30:1.00</td></tr><tr><td>June 30, 2007</td><td>1.30:1.00</td></tr><tr><td>September 30, 2007</td><td>1.35:1.00</td></tr><tr><td>December 31, 2007</td><td>1.40:1.00</td></tr><tr><td>March 31, 2008</td><td>1.40:1.00</td></tr><tr><td>June 30, 2008</td><td>1.40:1.00</td></tr><tr><td>September 30, 2008</td><td>1.40:1.00</td></tr><tr><td>December 31, 2008</td><td>1.40:1.00</td></tr><tr><td>March 31, 2009</td><td>1.40:1.00</td></tr><tr><td>June 30, 2009 (and each fiscal quarter thereafter)</td><td>1.50:1.00</td></tr></table>
<table><tr><td></td><td colspan="2">Pension Benefits</td><td colspan="2">Retiree Medical and Other Postretirement Benefits</td></tr><tr><td></td><td>2016</td><td>2015</td><td>2016</td><td>2015</td></tr><tr><td></td><td colspan="4">(In millions)</td></tr><tr><td>Benefit obligation at beginning of period</td><td>$16,395</td><td>$17,594</td><td>$1,131</td><td>$1,325</td></tr><tr><td>Service cost</td><td>2</td><td>2</td><td>3</td><td>3</td></tr><tr><td>Interest cost</td><td>749</td><td>737</td><td>47</td><td>50</td></tr><tr><td>Actuarial (gain) loss<sup>(1) (2)</sup></td><td>729</td><td>-1,159</td><td>-105</td><td>-177</td></tr><tr><td>Plan amendments</td><td>—</td><td>—</td><td>7</td><td>—</td></tr><tr><td>Settlements</td><td>-2</td><td>-3</td><td>—</td><td>—</td></tr><tr><td>Benefit payments</td><td>-635</td><td>-776</td><td>-92</td><td>-94</td></tr><tr><td>Other</td><td>—</td><td>—</td><td>—</td><td>24</td></tr><tr><td>Benefit obligation at end of period</td><td>$17,238</td><td>$16,395</td><td>$991</td><td>$1,131</td></tr><tr><td>Fair value of plan assets at beginning of period</td><td>$9,707</td><td>$10,986</td><td>$253</td><td>$244</td></tr><tr><td>Actual return on plan assets</td><td>915</td><td>-506</td><td>22</td><td>-10</td></tr><tr><td>Employer contributions</td><td>32</td><td>6</td><td>83</td><td>89</td></tr><tr><td>Settlements</td><td>-2</td><td>-3</td><td>—</td><td>—</td></tr><tr><td>Benefit payments</td><td>-635</td><td>-776</td><td>-92</td><td>-94</td></tr><tr><td>Other<sup>-3</sup></td><td>—</td><td>—</td><td>—</td><td>24</td></tr><tr><td>Fair value of plan assets at end of period</td><td>$10,017</td><td>$9,707</td><td>$266</td><td>$253</td></tr><tr><td>Funded status at end of period</td><td>$-7,221</td><td>$-6,688</td><td>$-725</td><td>$-878</td></tr></table>
<table><tr><td></td><td>Mainline  Operations</td><td>Wholly-owned  Regional Carriers</td><td>Total</td></tr><tr><td>Pilots and Flight Crew Training Instructors</td><td>13,400</td><td>3,400</td><td>16,800</td></tr><tr><td>Flight Attendants</td><td>24,700</td><td>2,200</td><td>26,900</td></tr><tr><td>Maintenance personnel</td><td>14,900</td><td>2,000</td><td>16,900</td></tr><tr><td>Fleet Service personnel</td><td>16,600</td><td>3,500</td><td>20,100</td></tr><tr><td>Passenger Service personnel</td><td>15,900</td><td>7,100</td><td>23,000</td></tr><tr><td>Administrative and other</td><td>16,000</td><td>2,600</td><td>18,600</td></tr><tr><td>Total</td><td>101,500</td><td>20,800</td><td>122,300</td></tr></table>

Question: What's the average of Pension Benefits' benefit obligation at beginning of period in 2015 and 2016? (in million)
Answer: 16994.5