Ryanair is keen to restart Buzz flights

The deal had been due to be cleared by the Office of Fair Trading (OFT) on Tuesday.

But a decision has been delayed until 28 April, amid continuing competition concerns.

That would leave Ryanair just three days to complete staff training and other preparations before the planned relaunch of Buzz services.

Job threat

Both Ryanair and Buzz's parent company KLM have said they cannot envisage any problems in gaining approval for the deal.

But in a statement Ryanair warned it needed a decision urgently "in order to save the core operation of Buzz and preserve up to 130 jobs at a time of crisis in the aviation industry".

Without OFT approval, Ryanair can not legally operate Buzz services under the Ryanair umbrella.

Ryanair announced in January it would pay KLM 23.9 million euros (�16.5m) for Buzz.

Earlier this month, the Irish company announced a rescue plan for Buzz which would see 440 jobs lost but 13 routes saved.

Ryanair cancelled all Buzz flights in April to prepare for the relaunch.

OFT response

The OFT said it normally allowed 45 working days to make a ruling on a takeover, which would take it to 28 April.

"It is not a hard and fast rule - something may happen before then," an OFT spokesman told BBC News Online.

"But more to the point, Ryanair did not approach us with details.

"Normally, the parties will come to you with detailed statements on what they are planning to do.

"In this case, we approached Ryanair. That may explain why it may be taking longer than expected."

The spokesman said the OFT would be looking at Ryanair's decision to cut jobs and routes among other issues.