Why Does Deicing Delay Flights? What Happens While You Wait

What happens, step by step

Step	What is going on	Why it can take time
1. Boarding	Deicing is done as close to departure as possible, so passengers are often already on board	You may be on board for the whole delay
2. Waiting in line	Planes queue for deicing trucks or a deicing pad	Everyone needs it at once during a storm
3. Deicing	Fluid removes frost, ice or snow to give clean surfaces	Heavier snow means more spraying
4. Anti-icing	A second fluid can protect the clean surfaces for a limited time	Required in some conditions
5. Holdover time starts	The clock starts when the final fluid application begins	Taxi and runway lines eat into it
6. Check or re-spray	If the time runs out, the plane must be checked or deiced again	Back into the line
7. Takeoff

Definitions from FAA Advisory Circular 120-60 and 14 CFR 121.629.

Deicing vs anti-icing

These are two different jobs. The FAA defines deicing as removing frost, ice or snow from the aircraft to give clean surfaces, and anti-icing as a precaution that protects treated surfaces against new frost, ice or snow for a limited period (FAA AC 120-60).

The same advisory circular describes two approaches:

• One-step: a single fluid both removes the ice and stays on to give limited protection.
• Two-step: deicing first, then a separate anti-icing application once the surfaces are clean, which gives the maximum possible protection.

It also explains the fluid types. Type I fluid is unthickened, forms a thin film and has very limited holdover time. Thicker fluids, such as the Type II fluid the circular describes, give longer holdover times; they form a gel-like film that flows off the wing as air moves over it during the takeoff run (FAA AC 120-60). If you have a window seat, that is the liquid you may see sliding off the wing as you speed down the runway.

The holdover clock: why you might get deiced twice

Holdover time is the estimated time the fluid will keep frost, ice and snow from building up on the protected surfaces. Under federal rules, it begins when the final application of fluid starts and ends when the fluid loses its effectiveness (14 CFR 121.629). The FAA publishes updated holdover time tables each winter season (FAA), and the times depend on the fluid, the temperature and the type and intensity of precipitation.

If a plane passes its maximum holdover time before takeoff, the rule allows it to go only if one of these happens:

1. A pretakeoff contamination check confirms the wings, control surfaces and other critical surfaces are free of frost, ice and snow. FAA guidance says this check must be done within 5 minutes before takeoff begins.
2. An FAA-approved alternate procedure confirms the surfaces are clean.
3. The plane is deiced again and a new holdover time begins.

So a long line for the runway in heavy snow can send a plane back for another spray. That is a safety rule, not the crew being slow.

Your rights if you are stuck on the plane

DOT's tarmac delay rule applies while you wait on the ground at a U.S. airport (14 CFR 259.4):

Rule	Domestic flight	International flight
Chance to get off the plane	Before the delay passes 3 hours	Before the delay passes 4 hours
Food and drinking water	Within 2 hours of the start of the delay	Within 2 hours
Working lavatories and medical help if needed	Throughout	Throughout
Status updates	Once the delay passes 30 minutes	Once the delay passes 30 minutes

There are exceptions: the deplaning deadline does not apply if the pilot decides it would be unsafe, or if air traffic control says returning to the gate would significantly disrupt airport operations. Food and water can also be withheld if the pilot decides safety or security prevents service.

Tips for a deicing day

• Use the restroom and fill a water bottle at the gate. Service may pause while the plane is in line.
• Charge your phone before boarding. Waits can be long.
• Build in connection time. On snowy days, a tight connection is the first thing to break.
• Watch the airline app. Gate and departure times can change while you wait. If you are planning winter travel with a coat, our guide on packing a winter coat in a carry-on covers what counts against your bag allowance.