With my current position, I have access to samples of ATC recordings, including all the flight plans received by a FIR. Parsing these recordings, I noticed that Ryanair always put the following sentence in both ICAO field F18/RMK and ADEXP field -RMK:
PAX SCHEDULED FLIGHT CONTACT +353 IRISH PHONE NUMBER
Why does Ryanair do that?
Note: the field "flight type" is also filled, and contains the letter S for Scheduled, thus my surprise. Note2: +353 is country code for Ireland where Ryanair is based.