United flies last 737
Flight 737, operated by 737-300 N331UA, took off from Washington Dulles and made what amounted to a farewell tour with stops at all the carrier’s hubs – Chicago, Denver and Los Angeles, with the final touchdown at its San Francisco maintenance base. United – which alongside Lufthansa was a launch customer for Boeing’s narrowbody workhorse – introduced the 737-200 into revenue service on 28 April 1968, and added the -300 model in 1986 and the -500s in 1990.

