Norwegian Air Shuttle, whose financial difficulties have been exacerbated by the coronavirus shutdowns, announced Monday that it had cancelled an order for 92 Boeing 737 Max aircraft and five Dreamliners.

It also said it had launched legal action to get compensation for the losses incurred after 737 MAXs were grounded worldwide in March 2019 following two deadly crashes, and to get down-payments on orders refunded.

The grounding of its 737s had "disrupted NAS' operations and caused significant losses", said the company's statement.

There had also been reliability problems with the Rolls Royce engines of the 787 aircraft, which had caused further losses, it said.

The company had been in talks with Boeing to reach a settlement, but had so far not reached an agreement on compensation, the statement added.

The announcement came as US regulators launched a test flight of the Boeing 737 MAX Monday, a key step in recertifying the jet so it can resume flights.

The MAX has been grounded globally since March 13, 2019, following an Ethiopian Airlines crash that killed 157 people. That catastrophe came just a few months after a Lion Air MAX crash that killed 189 people.