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London’s Piccadilly line, the Tube line that serves Heathrow Airport, is due to start carrying passengers on new air conditioned trains between December 2026 and June 2027. Transport for London says 94 new Siemens trains will replace the 86 trains that have run on the line since 1975, with walk-through carriages, wider doors and about 10 percent more space per train.
If you fly into Heathrow this winter or next spring, you may ride one of the first new trains, but most services will still use the older fleet at first. Keep an eye on weekend closures, which TfL needs to finish the upgrade, and check the TfL Piccadilly line upgrade page and journey planner before you travel.
If you are planning time in the city, our Tower of London guide covers tickets, timing and how to plan a visit.
- When: new trains enter service December 2026 to June 2027.
- Fleet: 94 new trains replace 86 from 1975.
- Cooling: first air conditioned deep level Tube trains.
- Space: about 10 percent more per train.
- Later: 27 trains an hour instead of 24.
What the New Piccadilly Line Trains Offer
TfL said in a July update on the upgrade that the new trains will have walk-through carriages, air conditioning, wider double doorways, four dedicated wheelchair spaces, better digital displays and onboard CCTV. They are lighter than the current trains but carry about 10 percent more people each.
Time Out reported on September 29 that the trains, built by Siemens in Goole, Yorkshire, place the cooling equipment under the floor to fit the line’s narrow tunnels, and use regenerative braking that produces less heat. It said only about 40 percent of the Tube network is currently air conditioned, and that temperatures on the Piccadilly line have reached 33 degrees Celsius during heatwaves.
Time Out explained why cooling deep level lines has been so hard. The tunnels are narrow, the surrounding London clay holds heat, and building new ventilation shafts means digging through property above ground. Placing the air conditioning under the floor is how the new trains get around those limits, which should make summer trips to and from Heathrow noticeably more comfortable once the fleet is in place.
When You Will Ride Them
TfL gives a window of December 2026 to June 2027 for the new trains to enter service, and Time Out described them as expected by Christmas. New fleets usually arrive a few trains at a time, so early on you are more likely to board an older train than a new one. By the end of the rollout, the whole line should use the new fleet.
TfL also plans to raise frequencies from 24 to 27 trains an hour, which it says will add 23 percent more capacity at peak times in central London. It has not tied that increase to a specific date, and it depends on other work along the line, including upgrades to track, trackside equipment, power systems and the depots at Cockfosters and Northfields.
| If you… | What to do |
|---|---|
| Land at Heathrow on a weekend | Check for Piccadilly line closures first. |
| Travel with large bags | Expect wider doors on new trains. |
| Visit London in summer 2027 | Expect cooler trains on most services. |
| Need step free access | Check TfL station information. |
Heathrow Travel During the Upgrade
The Piccadilly line is the cheapest rail link between Heathrow and central London, but it has had a run of weekend closures while TfL tests the new trains and upgrades the line. When the line is closed, the Elizabeth line and Heathrow Express are the main rail alternatives, and both usually cost more. Allow extra time on weekends and check the status of every line you plan to use on the day. TfL’s journey planner shows planned closures weeks ahead, so look before you book an early flight home.
If you arrive late at night or early in the morning, check first and last train times as well as any closures. With large luggage, the wider doors and walk-through carriages on the new trains should make boarding easier once they are running. The same planning applies on the way back to the airport, so leave margin for your flight.
Recent Piccadilly Line Closures
The upgrade has meant several closures this autumn. We covered them in our stories on the October 31 to November 1 Piccadilly line closure and the Heathrow weekend closure.
December 2026. First new trains due to enter service.
June 2027. End of the entry into service window.
27 trains an hour. TfL’s later frequency target.
When will the new Piccadilly line trains start running?
TfL says between December 2026 and June 2027.
Will the new Piccadilly line trains have air conditioning?
Yes. They will be the first deep level Tube trains with air conditioning.
Does the Piccadilly line go to Heathrow?
Yes. It links Heathrow Airport with central London.
How many new trains are there?
94 new trains will replace the current fleet of 86.
