Ryanair has today warned passengers that its online check-in service will not be available for 10 hours this weekend due to essential maintenance. Representatives for the budget airline have appealed to all passengers travelling on Friday and Saturday to check-in online for their flight on or before Thursday, June 18th. The website and mobile app will both be unavailable from 7pm Friday evening through to 5am Saturday morning for a systems upgrade. New bookings or changes to existing flights will not be possible during this web closure either. Ryanair is contacting all intending customers travelling on Friday 19^th and Saturday 20^th June by email and SMS text to advise them to check in online on or before Thursday June 18th so as to avoid this disruption. Ryanair's Robin Kelly said: “We sincerely apologise for any inconvenience caused by this upgrade, which will further improve Ryanair.com, Europe’s largest travel website.”