A quick search over at JetPhotos.net’s aircraft census database shows 94 active Boeing 737s in the United Airlines fleet. To peruse the list, click the link above and then select United, Boeing, 737, and check active, then click search. According to the database, the oldest active plane is a N301UA, a 737-322 delivered on Nov. 12, 1986. The newest plane of the soon-to-be-retired fleet is N942UA, a 737-522 delivered on Oct. 28, 1996.