Train engineer Brandon Bostian was alone at the controls last week when an Amtrak commuter train derailed in Philadelphia, killing eight people and injuring more than 200 others. Now, the union for Amtrak’s locomotive engineers is urging the rail service to put a second crew member in the control cab of trains traveling along the Northeast Corridor line.

“The public would never accept an airline operation with a single person in the cockpit. There is no reason that rail employees and rail passengers’ lives should be viewed any differently,” the Brotherhood of Locomotive Engineers and Trainmen said in a statement Tuesday afternoon.

Amtrak hasn’t required a second crew member to ride in the locomotive of Northeast Corridor trains since 1981, when Congress ended the two-person policy. The union said it has “steadfastly maintained” that Congress should reinstate the requirement, and it blamed lawmakers for underfunding Amtrak and making it difficult to hire additional crew members. “So long as those in Congress see fit to underfund the operation, they undermine their own mandate and shortchange the safety of the traveling public,” the statement said.

The National Transportation Safety Board, an independent federal agency, has still not determined a probable cause for the May 12 crash. Train 188 was going more than double the 50 mph limit around a sharp curve when it derailed, just 10 minutes after departing from Philadelphia for New York. Investigators said Bostian told them he couldn’t remember anything from the last 3 miles before the train came off the tracks.

Five crew members were aboard Train 188, but they were in the passenger coaches and closed off from the locomotive’s control cab, the Associated Press reported. The conductor, Emilio Fonseca, suffered a broken neck and broken back during the crash and remains hospitalized. Fonseca is among a handful of passengers on the commuter train who are suing Amtrak for “serious and disabling” injuries.

Amtrak didn’t immediately provide AP with a comment on the union’s request Tuesday. The union represents more than 55,000 professional locomotive engineers and trainmen throughout the United States.