United Airlines (UA, Chicago O'Hare) has disclosed in its quarterly investor update that it has signed a firm contract for nineteen second-hand B737-700s deliveries of which will start in December 2019 and run through to 2021.

The carrier did not reveal the aircraft's source though the incoming jets will likely be used to mitigate the absence of its grounded fleet of fourteen B737-9s.

According to the ch-aviation fleets advanced module, United currently operates forty B737-700s. Its narrowbody fleet also includes 141 B737-800s, twelve B737-900s, 136 -900(ER)s, seventy-four A319-100s, and ninety-nine A320-200s. It also has purchase agreements for twenty used A319s with expected delivery dates through 2022.

United is currently the world's third-largest operator of the B737-700, behind Southwest Airlines (WN, Dallas Love Field) with 513 units and WestJet (WS, Calgary) with fifty-three.