Heathrow Terminal 4 reopens after hazmat scare, evacuation triggers delays amid Tube strikes

An evening evacuation at Heathrow Terminal 4 forced check-in to empty, trains to halt, and passengers to turn back after a suspected hazardous materials incident. A few hours later, emergency services declared the area safe and the terminal reopened, but the timing—landing on a day of London Underground strikes—amplified the disruption across flights and onward connections.

What happened and how it unfolded

The London Fire Brigade was called at 5:01pm on Monday. Crews from Feltham, Heathrow, Wembley, and nearby stations responded, following a standard hazardous materials protocol: isolate the area, evacuate the public, test the air, and identify any contamination. Terminal 4’s check-in area was cleared as a precaution while specialist teams assessed the scene.

During the response, passengers were told not to travel to Terminal 4, and National Rail Enquiries said trains could not call at the terminal. That left travelers with fewer options at the worst possible moment, with Tube strikes already reducing capacity and forcing detours. Ground operations paused in the affected area while airline staff worked to hold flights where possible and retime departures where they couldn’t.

Transport Secretary Heidi Alexander posted on X that emergency services were on site and that she was monitoring updates from responders and the airport, urging passengers to avoid Terminal 4 until further notice. The guidance remained in place until fire crews and airport teams finished their checks and gave the all-clear. Once the terminal was declared safe, passengers were allowed back and normal operations resumed.

Here’s the key timeline based on official updates and airport operations:

• 5:01pm: Fire crews are called to Terminal 4 over a potential hazardous materials incident.
• Shortly after: The check-in area is evacuated; trains stop serving the terminal.
• Evening peak: Airlines begin to push back departures and hold some arrivals, depending on stand availability and safety cordons.
• Later in the evening: Emergency services complete testing and stand down the incident; Terminal 4 reopens.

Hazardous materials alerts at airports can be triggered by many things—leaking containers, strong odors, or mislabeled items. The goal is to overreact in the short term to avoid underestimating a risk. In practice, that means swift evacuations, broad cordons, and precise air-quality checks. Most incidents end with an all-clear after targeted testing, which is what happened here.

Delays, ripple effects, and what travelers can do

FlightRadar24 data showed knock-on delays across multiple airlines using Terminal 4. Qatar Airways had three delayed departures, while Etihad pushed back two flights to Abu Dhabi. Those setbacks matter because both airlines run large connecting banks in Doha and Abu Dhabi; miss the first leg and you often miss the connection, which then cascades into re-bookings and overnight stays.

Even after reopening, the disruption didn’t vanish. Crews and aircraft end up out of position, and restricted train access slowed passenger flow. Airlines typically triage: long-haul departures with full loads and tight connections get priority, while some short-haul and late-evening services slide to later times. Baggage handling can lag as ground teams reset from the evacuation.

Travel options were squeezed by Tube strikes. With trains to Terminal 4 temporarily halted and the Underground running on a reduced schedule, the normal Plan B—switch to the Tube—wasn’t reliable. That made road traffic around Heathrow heavier than usual, added pressure on taxi ranks, and left some travelers arriving after gate closure times. Expect residual delays on the first wave of morning flights if crews timed out or if aircraft overnighted out of sequence.

So what should passengers do after an evacuation like this?

• Re-check your booking: Use your airline’s app or call center to confirm your new departure time and gate before you leave home.
• Build in extra time: Security queues can spike after a restart. Aim to arrive earlier than usual until operations settle.
• Know your rights: Under UK261 rules, airlines owe duty of care during long delays—meals, communication, and hotel if you’re stranded overnight—though compensation may not apply if the cause is classed as an extraordinary circumstance.
• Protect your connection: If you’re connecting via Doha, Abu Dhabi, or another hub, ask the airline to move you to the next viable itinerary. They can often see options you can’t.

Terminal 4 serves a cluster of long-haul and full-service carriers, including Qatar Airways and Etihad, so any pause hits premium cabins, tight business itineraries, and complex connections. That’s why even a short evacuation ripples outward: one missed bank at a hub can reverberate through schedules for a day or more.

This incident lands after a difficult year for Heathrow’s resilience. Months ago, a major electrical substation fire forced widespread cancellations—about 1,300 flights in total—highlighting how one point of failure can shut down the busiest airport in the UK. Yet demand hasn’t softened. On August 1, Heathrow recorded its busiest day ever with 270,869 passengers across its four terminals. In July, the airport handled 7,981,137 passengers, only a touch higher than the same month in 2024, a sign of persistent capacity limits rather than weak demand.

Those numbers explain the stakes. When a terminal stops, even briefly, the system has little slack. Stand space gets tight, turnarounds lengthen, and crews hit legal duty limits. Add staff shortages in parts of the ground operation and the result is what passengers saw on Monday: a fast safety response, a cautious reopening, and a rest of day filled with delays.

For the airport, the playbook is now familiar: isolate the affected zone, lean on real-time testing equipment, coordinate with airlines on revised blocks and pushbacks, and keep passengers informed. For travelers, the best move is to assume the schedule will wobble for a few hours after any all-clear and to plan around it—especially when citywide transport is also under strain.

By late evening, Terminal 4 was back in action with no ongoing safety concerns reported by emergency services. Normal operations don’t mean normal experiences right away, though. Expect some aircraft and crew to be in the wrong place through the night, with airlines ironing that out flight by flight. If you’re flying today, keep your phone charged, watch for gate changes, and give yourself a bit more runway to get to the gate on time.