Exhibit 10.4 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT IS BOTH NOT MATERIAL AND IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. OMITTED INFORMATION HAS BEEN REPLACED WITH ASTERISKS. Supplemental Agreement No. 1 to Purchase Agreement No. 03776 between The Boeing Company and United Continental Holdings, Inc. Relating to Boeing Model 737-9 Aircraft THIS SUPPLEMENTAL AGREEMENT, entered into as of June 17, 2013, by and between THE BOEING COMPANY (Boeing) and UNITED CONTINENTAL HOLDINGS, INC. (Customer); WHEREAS, the parties hereto entered into Purchase Agreement No. 03776 dated July 12, 2012, as amended and supplemented (the Purchase Agreement), relating to the purchase and sale of Boeing Model 737-9 aircraft (Aircraft). This Supplemental Agreement is an amendment to the Purchase Agreement; WHEREAS, Boeing and Customer have agreed to *** Aircraft *** scheduled for delivery from *** through *** (MAX *** Aircraft); WHEREAS, Boeing and Customer agree that 787-10 Model aircraft program launch requires approval from the Boeing Board of Directors, pursuant to Letter Agreement as detailed in Letter Agreement UAL-PA-03860-LA-1301380. WHEREAS, Boeing and Customer agree that the MAX *** Aircraft will be ***; NOW THEREFORE, in consideration of the mutual covenants herein contained, the parties agree to amend the Purchase Agreement as follows: 1. Table of Contents and Tables: 1.1 Remove and replace, in its entirety, the “Table of Contents,” with the “Table of Contents” attached hereto, to reflect the changes made by this Supplemental Agreement No. 1. UCH-PA-03776 SA-1, Page 1 BOEING/UNITED CONTINENTAL HOLDINGS, INC. PROPRIETARY �      �    �     � !" # $% ! &�  %'   ! ( )*+,-.-*+/01232,2+.4$"5%% ! &�6%  ! &789:;! < =(>+-.2,4  !?@8@   (>AB0C13DE/2AF122G2+.4;! <H"5%% ! &86%  ! &I8I()AB0C13DE/2AF122G2+.4;! <  !;!?@8@   ;! <H"5%% ! &�6%  ! H<  J6 ! %5        %%%  K  !  ! %  !L"M"J<"#=&#<6N=J"        OPQRSQTUV)SW0AUX  >UTOQY)SUOTUQUOABPSBYTUVZ[TU)\]]]  ̂̂_ N   ! %    ! %  ̀     a6 b̀    %     <Jc6:7@@9   �6 !  RSQTUVd>UTOQY)SUOTUQUOABPSBYTUVZ[TU)\0eS0eTQOAeX  �  � �    �     !!"#$  %  "&'(! )  * +  *, -  !! .,# �    /0102345360724/65�289:;<=<>?   >@AB�    CD CE  F  C"&GH,#!G#$ #I# JJ  �AB�  K  K# !L#,MC,!N$ O# FOK  FOKPI# D'  D# ,'$$ PI# KK  KEQRRR 'S*  '&SC* D ,$ # ��T  �  UDVW*WX)YYZWSW%XYZ)Y  [[[ 24:0\ UDVW*WX)YYZWSW%XYZ)]  RRR UDVW*WX)YYZWSW%XYZ+X  ", # OE(Q& UDVW*WX)YYZWSW%XYZ+)  N$# UDVW*WX)YYZWSW%XYZ++  N$ C UDVW*WX)YYZWSW%XYZ+Z  * ,  '$$  UDVW*WX)YYZWSW%XYZ+Y  '*(#!KH$, UDVW*WX)YYZWSW%XYZ+̂  '$*#_* &# E UDVW*WX)YYZWSW%XYZ-X  '$# UDVW*WX)YYZWSW%X]X--  RRR UDVW*WX)YYZWSW%X]%%  RRR UDVW*WX)YYZWSW%X]%)  RRR# UDVW*WX)YYZWSW%X]-Y  RRR UDVW*WX)YYZ   'W*E C% .FSKNODǸ .K̀ .'   Ta �b  �  �Bb Tc dJJ�e  �  � �  �    �� �  !"##$% &'!('")  *+,+-./.0120324+0.25+1-615.*7  !"##$% &'!(89$  :; 615.*7  !"##$% &'!('"(  77+/2<.25615.*7  !"##$% &'!(($9  =.-+,.*>???615.*7  % !"#($% &'!#($9 #"#*30@A5+32 0B@75<.257 CC � �  �DDEFGEHIF JKJJJJJJJJJJJJJ  LKMNOKP !"##$   Q &R1/.'34' ; S%TUVUW;TW;Q   X �  �  �Y  JCC �Z 

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