Rail firm GNER faces an uncertain future as its parent company approaches a deadline to repay huge debts, according to unions.
Sea Containers Ltd has until Sunday to pay off debts of £60m.
The RMT union says GNER, which signed a 10-year franchise in 2005 to run trains on the East Coast Mainline, may have to cut jobs.
But the firm said it had overcome some recent challenges and is now seeing record numbers of passengers.
Allen Heath, of the RMT said: "I think it's inevitable, when you consider the position GNER is in, they frankly are not making anywhere near the sort of profits they allowed for in the franchise.
"Something's got to give and the only thing that can give really is jobs."
Jonathon Metcalfe, chief executive of GNER, said the company had faced some challenges since it took over the franchise, but was now achieving some positive results.
He said: "It's well known that we do have some challenges and we did get some unexpected events in the first year of the franchise, but everyone's working very hard to recover from that and we're now seeing record numbers of passengers, about 17 million a year."