The nearest airport is Birmingham (BHX) which serves most major airlines and many smaller ones too. It’s about a 20 minute taxi journey from the airport to WBS. Alternatively, it is a short monorail ride from the airport terminal to Birmingham International rail station, where you can catch a train to Coventry railway station.
Many international flights travel to and from the following London airports:
London Heathrow (LHR) - about 2.5 hours away
London Gatwick (LGW) - about 3.5 hours away
London Stansted (STN) - about 3.5 hours away