Heathrow Express plans to run services every 15 minutes during shortened operating hours if a threatened 24-hour walk-out by Network Rail workers goes ahead from 17:00 on Bank Holiday Monday. Should the RMT and TSSA unions’ strike by signallers and maintenance staff take place, on Monday the normal Heathrow Express timetable will be in operation until 18:30, and on Tuesday services will run between 07.30 and 18:30.