Exhibit 10.10 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. 6 to Purchase Agreement No. 03776 between The Boeing Company and United Airlines, Inc. Relating to Boeing Model 737-9 Aircraft THIS SUPPLEMENTAL AGREEMENT, entered into as of February 8, 2016, by and between THE BOEING COMPANY (Boeing) and UNITED AIRLINES, INC. (Customer); WHEREAS, the parties hereto entered into Purchase Agreement No. 3776 dated July 12, 2012, as amended and supplemented (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 agree to *** firm model 737-9 Aircraft with *** model 737-9 *** Aircraft in the same delivery month: Aircraft Delivery Month * * * WHEREAS, Boeing and Customer agree to *** such 737-9 firm aircraft with *** firm 737-*** aircraft under ***. WHEREAS, Boeing and Customer agree to apply *** firm model 737-9 Aircraft terminated under this Supplemental Agreement No. 06 (i) first to the *** Deposit for the *** new model 737-9 *** Aircraft added under this Supplemental Agreement No. 06 and (ii) then towards Customer's ***. UAL-PA-03776 SA-6 Page 1 BOEING / UNITED AIRLINES, INC. PROPRIETARY � ! !" ! # $ ! !" ! " #%& ' ( # ) " ! * ( # )+ ! "" ! ! ! , " " %! " * ( # )+ -!"!#!" (, *�.+/ 0 (* ( '+ 12134 567879:; <=>6?=7@A <=B876C;6DEA F768= 9EG HHH ! "" ! ! ! , " " %! "!! , !" * ( '+ -!"!#!" (, *�.+/ I * I J)...I.'0KK+ ! "" ! ! ! , " " %! " * I J)...I.'0KK+ -!"!#!" (, *�.+/ %! ( "" " L $!"" ! # " # " " %!! ! # # " # MNO POQR ST RNUQ VWXO UQ YOTR UZROZRUSZWY[ \YWZ]̂ JI.. �. 0_̀ abcd e fcbgah ibjkbcalm bcno pj̀ pjbagijq � ! " # " # !$ % $ &' ()* +,*-./ 0,123.4 5.-(*6 3-78-.*9: -.0;<< = << > " " �$ �$ = > " " $" $" #?$?@ �$ A$ $" B @$ " $ $! @$ $ C!$ $ $ ?? �? +,*-./ D 5.-(*6 3-78-.*9: -.0; 27,27-*(374 � � � � !!"#$ % "&'(! ) * + *, - !! .,# � /0 12324567582946187�4:;<=>?>@A @BCD� EF EG H E"&IJ,#!I#$ #K# LL �CD� M M# !N#,OE,!P$ Q# HQM HQMRK# F' F# ,'$$ RK# MM MGSTTT 'U* '&UE* F ,$ # ��V � WFXY*YZ)[[\YUY%Z[\)[ TTT# WFXY*YZ)[[\YUY%Z[\)] TTT WFXY*YZ)[[\YUY%Z[\+Z ", # QG(S& WFXY*YZ)[[\YUY%Z[\+) P$# WFXY*YZ)[[\YUY%Z[\++ P$ E 'Y+ ̂ 61871232456@643_9<76 @BWFXY*YZ)[[\YUY%Z[\+\ * , '$$ WFXY*YZ)[[\YUY%Z[\+[ '*(#!MJ$, WFXY*YZ)[[\YUY%Z[\+̀ '$*#a* &# G WFXY*YZ)[[\YUY%Z[\-Z '$# WFXY*YZ)[[\YUY%Z]Z-- TTT WFXY*YZ)[[\YUY%Z]%% TTT WFXY*YZ)[[\YUY%Z]%) TTT# WFXY*YZ)[[\YUY%Z]-[ TTT WFXY*YZ)[[\ .HUMPQFPb.Mb.' 'Y\*G E% Vc �d e 0LL�f
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