The regional airline Flyglobespan has had one of its flying licences suspended as a result of serious concerns about its operations.
Flyglobespan has started providing flights to North America
Several of the Edinburgh-based firm's services to North America have been affected.
The firm has had its 'ETOPS' license, which lets it fly over large expanses of water with two engines, suspended.
The Civil Aviation Authority (CAA) said it is the first time in 15 years a UK operator has lost ETOPS approval.
But the CAA declined to give specific reasons as to why the license had been suspended but said suspending ETOPS approval "is not done lightly".
A spokesman for Flyglobespan said that ETOPS approval has only been suspended on a temporary basis, and that this was because of an isolated problem with subcontractors.
A statement given to the BBC by the CAA said: "On Friday 12 October, we provisionally suspended the airline's ETOPS approval. We will be meeting with the airline later this week to review this decision."
The airline mainly flies from Scotland, including from Glasgow, Aberdeen, and Edinburgh airports and from northern England, including Durham and Newcastle. North American destinations include Calgary, Toronto, Boston and New York.
On transatlantic routes, twin-engine planes without ETOPS clearance are forced to adopt a flight path which never takes them more than an hour away from the nearest airport, in case of engine problems.
European flights do not involve straying more than an hour away from the nearest airport, so no ETOPS licence is needed to operate these flights.
But recently, Flyglobespan has expanded into North America and it is these services which could be affected by the loss of ETOPS.
Without ETOPS, the airline can only fly over the Atlantic via Iceland, Greenland and Canada - an indirect, slower route.
Longer flights burn more fuel, and cost the airline a significant amount of money.
The company says it is confident ETOPS approval will soon be restored.
As well as using its own aircraft on transatlantic routes, Flyglobespan leases aircraft and flight crews from other airlines which can continue to fly to the US.