Table of Contents NOTES TO CONSOLIDATED FINANCIAL STATEMENTS OF AMERICAN AIRLINES GROUP INC.
Secured financings are collateralized by assets, primarily aircraft, engines, simulators, rotable aircraft parts, airport leasehold rights, route authorities and airport slots.
At December 31, 2015, the Company was operating 35 aircraft under capital leases.
Leases can generally be renewed at rates based on fair market value at the end of the lease term for a number of additional years.
At December 31, 2015, the maturities of long-term debt and capital lease obligations are as follows (in millions):
## Table 0 ##
(a) 2013 Credit Facilities On June 27, 2013, American and AAG entered into a Credit and Guaranty Agreement (as amended, restated, amended and restated or otherwise modified, the 2013 Credit Agreement) with Deutsche Bank AG New York Branch, as administrative agent, and certain lenders that originally provided for a $1.9 billion term loan facility scheduled to mature on June 27, 2019 (the 2013 Term Loan Facility) and a $1.0 billion revolving credit facility scheduled to mature on June 27, 2018 (the 2013 Revolving Facility).
The maturity of the term loan facility was subsequently extended to June 2020 and the revolving credit facility commitments were subsequently increased to $1.4 billion with an extended maturity date of October 10, 2020, all of which is further described below.
On May 21, 2015, American amended and restated the 2013 Credit Agreement pursuant to which it refinanced the 2013 Term Loan Facility (the $1.9 billion 2015 Term Loan Facility and, together with the 2013 Revolving Facility, the 2013 Credit Facilities) to extend the maturity date to June 2020 and reduce the LIBOR margin from 3.00% to 2.75%.
In addition, American entered into certain amendments to reflect the ability for American to make future modifications to the collateral pledged, subject to certain restrictions.
The $1.9 billion 2015 Term Loan Facility is repayable in annual installments, with the first installment in an amount equal to 1.25% of the principal amount commencing on June 27, 2016 and installments thereafter, in an amount equal to 1.0% of the principal amount, with any unpaid balance due on the maturity date.
As of December 31, 2015, $1.9 billion of principal was outstanding under the $1.9 billion 2015 Term Loan Facility.
Voluntary prepayments may be made by American at any time.
On October 10, 2014, American and AAG amended the 2013 Credit Agreement to extend the maturity date of the 2013 Revolving Facility to October 10, 2019 and increased the commitments thereunder to an aggregate principal amount of $1.4 billion while reducing the letter of credit commitments thereunder to $300 million.
On October 26, 2015, American, AAG, US Airways Group and US Airways amended the 2013 Credit Agreement to extend the maturity date of the 2013 Revolving Facility to October 10, 2020.
The 2013 Revolving Facility provides that American may from time to time borrow, repay and reborrow loans thereunder and have letters of credit issued thereunder.
As of December 31, 2015, there were no borrowings or letters of credit outstanding under the 2013 Revolving Facility.
The 2013 Credit Facilities bear interest at an index rate plus an applicable index margin or, at American’s option, LIBOR (subject to a floor of 0.75%, with respect to the $1.9 billion 2015 Term Loan Facility) plus a LIBOR margin of 3.00% with respect to the 2013 Revolving Facility and 2.75% with respect to the $1.9 billion 2015 Term Loan Facility; provided that American’s corporate credit rating is Ba3 or higher from Moody’s and BB- or higher from S&P, the applicable LIBOR margin would be 2.50% for the $1.9 billion 2015 Term Loan131
PART II DUKE ENERGY CORPORATION ?
DUKE ENERGY CAROLINAS, LLC ?
PROGRESS ENERGY, INC.  ?
DUKE ENERGY PROGRESS, LLC ?
DUKE ENERGY FLORIDA, LLC ?
DUKE ENERGY OHIO, INC.  ?
DUKE ENERGY INDIANA, LLC ?
PIEDMONT NATURAL GAS COMPANY, INC.
## Table 1 ##
(a) Electric Utilities and Infrastructure includes an after-tax charge of $58 million related to the Edwardsport settlement.
Refer to Note 4 for further information.
(b) Other includes $60 million of after-tax costs to achieve mergers.
(c) Other includes after-tax charges of $77 million related to cost savings initiatives.
Refer to Note 19 for further information.
(d) Includes the impact of a settlement agreement reached in a lawsuit related to the Midwest Generation Disposal Group.
Refer to Note 5 for further information related to the lawsuit and Note 2 for further information on discontinued operations.
(e) Other includes capital investment expenditures of $45 million related to the International Disposal Group.
(f) Other includes Assets Held for Sale balances related to the International Disposal Group.
Refer to Note 2 for further information.
Geographical Information For the years ended December 31, 2017, 2016 and 2015, all assets and revenues from continuing operations are within the U. S.  Major Customers For the year ended December 31, 2017, revenues from one customer of Duke Energy Progress are $521 million.
Duke Energy Progress has one reportable segment, Electric Utilities and Infrastructure.
No other subsidiary registrant has an individual customer representing more than 10 percent of its revenues.
Products and Services The following table summarizes revenues of the reportable segments by type
## Table 2 ##
DUKE ENERGY CORPORATION ?
DUKE ENERGY CAROLINAS, LLC ?
PROGRESS ENERGY, INC.  ?
DUKE ENERGY PROGRESS, LLC ?
DUKE ENERGY FLORIDA, LLC ?
DUKE ENERGY OHIO, INC.  ?
DUKE ENERGY INDIANA, LLC ?
PIEDMONT NATURAL GAS COMPANY, INC.
## Table 3 ##
Transfers between levels represent assets or liabilities that were previously (i) categorized at a higher level for which the inputs to the estimate became less observable or (ii) classified at a lower level for which the inputs became more observable during the period.
The Duke Energy Registrant’s policy is to recognize transfers between levels of the fair value hierarchy at the end of the period.
There were no transfers between levels during the years ended December 31, 2017, 2016 and 2015.
In addition, for Piedmont, there were no transfers between levels during the two months ended December 31, 2016, and the years ended October 31, 2016, and 2015.
Valuation methods of the primary fair value measurements disclosed below are as follows.
Investments in equity securities The majority of investments in equity securities are valued using Level 1 measurements.
Investments in equity securities are typically valued at the closing price in the principal active market as of the last business day of the quarter.
Principal active markets for equity prices include published exchanges such as the New York Stock Exchange (NYSE) and the NASDAQ Stock Market.
Foreign equity prices are translated from their trading currency using the currency exchange rate in effect at the close of the principal active market.
There was no after-hours market activity that was required to be reflected in the reported fair value measurements.
Investments in debt securities Most investments in debt securities are valued using Level 2 measurements because the valuations use interest rate curves and credit spreads applied to the terms of the debt instrument (maturity and coupon interest rate) and consider the counterparty credit rating.
If the market for a particular fixed-income security is relatively inactive or illiquid, the measurement is Level 3.
Commodity derivatives Commodity derivatives with clearinghouses are classified as Level 1.
Other commodity derivatives, including Piedmont’s natural gas supply contracts, are primarily valued using internally developed discounted cash flow models that incorporate forward price, adjustments for liquidity (bid-ask spread) and credit or non-performance risk (after reflecting credit enhancements such as collateral) and are discounted to present value.
Pricing inputs are derived from published exchange transaction prices and other observable data sources.
In the absence of an active market, the last available price may be used.
If forward price curves are not observable for the full term of the contract and the unobservable period had more than an insignificant impact on the valuation, the commodity derivative is classified as Level 3.
In isolation, increases (decreases) in natural gas forward prices result in favorable (unfavorable) fair value adjustments for gas purchase contracts; and increases (decreases) in electricity forward prices result in unfavorable (favorable) fair value adjustments for electricity sales contracts.
Duke Energy regularly evaluates and validates pricing inputs used to estimate the fair value of natural gas commodity contracts by a market participant price verification procedure.
This procedure provides a comparison of internal forward commodity curves to market participant generated curves.
Interest rate derivatives Most over-the-counter interest rate contract derivatives are valued using financial models that utilize observable inputs for similar instruments and are classified as Level 2.
Inputs include forward interest rate curves, notional amounts, interest rates and credit quality of the counterparties.
Other fair value considerations See Note 11 for a discussion of the valuation of goodwill and intangible assets.
See Note 2 related to the acquisition of Piedmont in 2016 and the purchase of NCEMPA’s ownership interests in certain generating assets in 2015.
DUKE ENERGY The following tables provide recorded balances for assets and liabilities measured at fair value on a recurring basis on the Consolidated Balance Sheets.
Derivative amounts in the table below for all Duke Energy Registrants exclude cash collateral, which is disclosed in Note 14.
See Note 15 for additional information related to investments by major security type for the Duke Energy Registrants.
II The following table shows the percent changes in dekatherms delivered and average number of customers.
The percentages for all throughput deliveries represent billed and unbilled sales.
Amounts are not weather-normalized.

Tables referenced above, in order (Table 0 first):
<table><tr><td>2016</td><td>$2,266</td></tr><tr><td>2017</td><td>1,598</td></tr><tr><td>2018</td><td>2,134</td></tr><tr><td>2019</td><td>3,378</td></tr><tr><td>2020</td><td>3,587</td></tr><tr><td>2021 and thereafter</td><td>7,844</td></tr><tr><td>Total</td><td>$20,807</td></tr></table>
<table><tr><td></td><td colspan="7">Year Ended December 31, 2015</td></tr><tr><td>(in millions)</td><td>Electric Utilities and Infrastructure</td><td>Gas Utilities and Infrastructure</td><td>Commercial Renewables</td><td>Total Reportable Segments</td><td>Other</td><td>Eliminations</td><td>Total</td></tr><tr><td>Unaffiliated Revenues</td><td>$21,489</td><td>$536</td><td>$286</td><td>$22,311</td><td>$60</td><td>$—</td><td>$22,371</td></tr><tr><td>Intersegment Revenues</td><td>32</td><td>5</td><td>—</td><td>37</td><td>75</td><td>-112</td><td>—</td></tr><tr><td>Total Revenues</td><td>$21,521</td><td>$541</td><td>$286</td><td>$22,348</td><td>$135</td><td>$-112</td><td>$22,371</td></tr><tr><td>Interest Expense</td><td>$1,074</td><td>$25</td><td>$44</td><td>$1,143</td><td>$393</td><td>$-9</td><td>$1,527</td></tr><tr><td>Depreciation and amortization</td><td>2,735</td><td>79</td><td>104</td><td>2,918</td><td>135</td><td>—</td><td>3,053</td></tr><tr><td>Equity in (losses) earnings of unconsolidated affiliates</td><td>-2</td><td>1</td><td>-6</td><td>-7</td><td>76</td><td>—</td><td>69</td></tr><tr><td>Income tax expense (benefit)</td><td>1,602</td><td>44</td><td>-128</td><td>1,518</td><td>-262</td><td>—</td><td>1,256</td></tr><tr><td>Segment income (loss)<sup>(a)(b)(c)</sup></td><td>2,819</td><td>73</td><td>52</td><td>2,944</td><td>-299</td><td>—</td><td>2,645</td></tr><tr><td>Add back noncontrolling interest component</td><td></td><td></td><td></td><td></td><td></td><td></td><td>9</td></tr><tr><td>Income from discontinued operations, net of tax<sup>(d)</sup></td><td></td><td></td><td></td><td></td><td></td><td></td><td>177</td></tr><tr><td>Net income</td><td></td><td></td><td></td><td></td><td></td><td></td><td>$2,831</td></tr><tr><td>Capital investments expenditures and acquisitions<sup>(e)</sup></td><td>$6,852</td><td>$234</td><td>$1,019</td><td>$8,105</td><td>$258</td><td>$—</td><td>$8,363</td></tr><tr><td>Segment assets<sup>(f)</sup></td><td>109,097</td><td>2,637</td><td>3,861</td><td>115,595</td><td>5,373</td><td>188</td><td>121,156</td></tr></table>
<table><tr><td>(in millions)</td><td>Retail Electric</td><td>Wholesale Electric</td><td>Retail Natural Gas</td><td>Other</td><td>Total Revenues</td></tr><tr><td>2017</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Electric Utilities and Infrastructure</td><td>$18,177</td><td>$2,104</td><td>$—</td><td>$1,050</td><td>$21,331</td></tr><tr><td>Gas Utilities and Infrastructure</td><td>—</td><td>—</td><td>1,732</td><td>104</td><td>1,836</td></tr><tr><td>Commercial Renewables</td><td>—</td><td>375</td><td>—</td><td>85</td><td>460</td></tr><tr><td>Total Reportable Segments</td><td>$18,177</td><td>$2,479</td><td>$1,732</td><td>$1,239</td><td>$23,627</td></tr><tr><td>2016</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Electric Utilities and Infrastructure</td><td>$18,338</td><td>$2,095</td><td>$—</td><td>$933</td><td>$21,366</td></tr><tr><td>Gas Utilities and Infrastructure</td><td>—</td><td>—</td><td>871</td><td>30</td><td>901</td></tr><tr><td>Commercial Renewables</td><td>—</td><td>303</td><td>—</td><td>181</td><td>484</td></tr><tr><td>Total Reportable Segments</td><td>$18,338</td><td>$2,398</td><td>$871</td><td>$1,144</td><td>$22,751</td></tr><tr><td>2015</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Electric Utilities and Infrastructure</td><td>$18,695</td><td>$2,014</td><td>$—</td><td>$812</td><td>$21,521</td></tr><tr><td>Gas Utilities and Infrastructure</td><td>—</td><td>—</td><td>546</td><td>-5</td><td>541</td></tr><tr><td>Commercial Renewables</td><td>—</td><td>245</td><td>—</td><td>41</td><td>286</td></tr><tr><td>Total Reportable Segments</td><td>$18,695</td><td>$2,259</td><td>$546</td><td>$848</td><td>$22,348</td></tr></table>
<table><tr><td></td><td colspan="5">December 31, 2017</td></tr><tr><td>(in millions)</td><td>Total Fair Value</td><td>Level 1</td><td>Level 2</td><td>Level 3</td><td>Not Categorized</td></tr><tr><td>NDTF equity securities</td><td>$4,914</td><td>$4,840</td><td>$—</td><td>$—</td><td>$74</td></tr><tr><td>NDTF debt securities</td><td>2,174</td><td>635</td><td>1,539</td><td>—</td><td>—</td></tr><tr><td>Other AFS equity securities</td><td>123</td><td>123</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Other trading and AFS debt securities</td><td>241</td><td>57</td><td>184</td><td>—</td><td>—</td></tr><tr><td>Derivative assets</td><td>51</td><td>3</td><td>20</td><td>28</td><td>—</td></tr><tr><td>Total assets</td><td>7,503</td><td>5,658</td><td>1,743</td><td>28</td><td>74</td></tr><tr><td>Derivative liabilities</td><td>-230</td><td>-2</td><td>-86</td><td>-142</td><td>—</td></tr><tr><td>Net assets (liabilities)</td><td>$7,273</td><td>$5,656</td><td>$1,657</td><td>$-114</td><td>$74</td></tr></table>

Question: In which year is Commercial Renewables in Total Revenues positive?
Answer: 2015; 2016; 2017