People using the Route X26 between Heathrow Central and West Croydon will see this bus renumbered to SL7.
The SL7 will double in frequency to one bus every 15 minutes instead of every 30 minutes.
Other improvements to follow on many of the buses include improved customer information, USB charging and luggage racks.
Buses on the SL7 route will call at the same stops, with some of the bus stop names changing to better reflect their locations.
This includes Wood Street, which will now become Kingston Wood Street.