Interest in Boeing’s 747-400 freighter family already was rebounding last year, even as Delta Air Lines Inc. and United Continental Holdings Inc. hosted nostalgic farewell tours to mark the end of U.S. passenger service on the four-engine behemoth nicknamed the “Queen of the Skies.” With Boeing’s factory-fresh models sold out through 2021, cargo carriers are snapping up jumbo freighters that were built from 1993 to 2009 — if they can find them.

The long-awaited extension of two runways at Alliance Airport is complete, clearing the way for the north Fort Worth’s privately run cargo airfield to expand its services to include companies wishing to ship freight as far away as Europe.

Boeing Co. is considering whether to convert used 777 passenger jets into freighters, seeking to capitalize as booming e-commerce sales spur new demand for airfreight worldwide, sources familiar with the matter said.