It's the letter Cillian Burns didn’t expect — a reply from Ryanair head honcho Michael O’Leary.

Cillian (11) wrote to Mr O’Leary to challenge his claim there were no noise issues with aircraft using George Best Belfast City Airport.

He described receiving “free 6.30am alarm calls” at his south Belfast home every day and invited Mr O’Leary to come and stay for a night to hear from himself — even promising free loo use!

The Ballynafeigh youngster had no real expectation of hearing back from Mr O’Leary until the letter dropped onto the doormat.

Cillian wrote after hearing a radio broadcast of O’Leary stating his belief that there was no noise issue with planes at the airport.

The Ryanair boss backs the airport’s plans to expand the runway.

Cillian told him that the noise was a daily problem for thousands living below the flightpath.

“Thanks to the City Airport we receive free 6.30am alarm calls every day of the week, Saturday and Sunday included,” he wrote.

“So, Mr O’ Leary, please consider my family’s offer to come and visit us for a night.”

In his reply, Mr O’Leary said: “Thank you for the invitation to come and stay in your house at night, but there is not much point in taking up the offer, since we don’t have any aircraft flying at night.

“I particularly appreciate your offer to use your loo for free and look forward to returning a similar service to you whenever you are next flying on Ryanair.”

Cillian’s dad Keith said: “We were disappointed that Michael O’Leary did dismiss the noise issue out of hand. But it was nice of him to reply back.”

Mr Burns said the peace and quiet since aircraft were grounded due to the volcanic ash cloud has been fantastic for the family.

“Michael O’Leary’s definition of night-time and most people’s would be two different things. Most people would think of 6.30am as still being night-time.”