Ryanair cut its summer 2020 growth rate to 3% from 7%, which means full year traffic growth for the year to March 2021 will be cut from 162 million passengers to around 157 million.

The airline expects the grounded aircraft to return to service before the end of the year, with the first of new aircraft ordered by Ryanair to be delivered in January and February 2020.

But the exact date is uncertain and Ryanair has revised its summer 2020 schedule based on 30 incremental aircraft, rather than 58. Ryanair is waiting to take delivery of the new MAX aircraft, which it can receive at a maximum rate of 6 to 8 per month.

"Boeing is hoping that a certification package will be submitted to regulators by September with a return to service shortly thereafter," Ryanair Chief Executive Michael O'Leary said in a statement.

"We believe it would be prudent to plan for that date to slip by some months, possibly as late as December," he said.

"As Ryanair have ordered the Boeing MAX200s, which are a variant of the MAX aircraft, these need to be separately certified by the FAA and EASA."

"Ryanair expects that the MAX200 will be approved for flight services within 2 months of the MAX return to service."