I take more than a passing interest in sports charters with Arsenal and Watford both using Luton for international and domestic flights with teams playing at both venues from Liverpool, Swansea etc. flying into Luton. As far as Arsenal are concerned (Europa League) there next match is in Moscow and if they reach the final that will be played in Lyon this year in May so that should have no effect. Regarding the Champions League only Manchester City and Liverpool are left in and playing each other in the next round. If Liverpool reach the final - to be played in Kiev - there could be a small number of charters from London airports but dare I say if Man City reach the final very few indeed.
Looking further ahead to the European Championships in 2020 both semi-finals and the final are to be played at Wembley. Also there is talk of the Super Bowl final being played at Wembley - that will be interesting!
Also Ruby Union teams (Saracens and Northampton) regularly fly from Luton as well as a number of charters involved in Formula One races in Europe. They all have to fly from somewhere in the south east.