Unite union said more than 2,000 of its members will walk out on 31 days over the summer, potentially throwing travellers' summer plans into disarray.

The strikes will coincide with the beginning of the school holidays and the August bank holiday.

Here's what you need to know.

Who is striking?

Security officers based at Terminal 3 and Terminal 5, as well as campus security, who are responsible for people and vehicles going airside.

Security officers are the people responsible for screening passengers and luggage, reading x-ray monitors and patrolling the airport.

What airlines will be affected?

The strikes will affect flights by a number of airlines including Virgin, Emirates, Qatar, United, American and Delta.

The walkouts at Terminal 5 will "heavily affect" British Airways's summer schedule, Unite said.

Will flights be delayed or cancelled?

Delays, disruption and cancellations will be "inevitable" as a result of the strike action, Unite regional co-ordinating officer Wayne King said, although it's too early to say what flights will be affected.

The union has also said the action could escalate.

The number of security officers on shift affects how many passengers can go through the airport - fewer staff means fewer passengers.

When security officers at Terminal 5 went on strike over Easter, British Airways was forced to cancel dozens of flights a day.

The airline also stopped selling tickets for strike days - so if you're yet to book your summer holiday, you may see your flight choices reduced.

A Heathrow spokesperson said: "Passengers can rest assured that we will do everything we can to minimise strike disruption so they can enjoy their hard-earned summer holidays."

I'm travelling through Heathrow on a strike day - what should I do?

People travelling on strike days should check their flight details and status before setting off for the airport in case of a last-minute change.

Heathrow's advice is to arrive two hours before short-haul flights and three hours before long-haul flights - no earlier.

On strike days, passengers are only allowed to take two items of hand luggage through security.

Expect the airport to be busy and queues to be longer than normal for security.

What are my rights if my flight is delayed or cancelled due to strikes?

As the Heathrow workers aren't employed by the airlines, your airline is not obliged to offer compensation.

However, they should offer you an alternative flight if yours is cancelled and provide assistance if your flight is delayed by more than two hours.

Why are workers striking?

The strikes are part of a long-running dispute over pay.

Heathrow security officers are paid about £5,000 to £6,000 less than their counterparts at Gatwick and Stansted, according to Unite.

Union members have rejected a pay rise of 10.1%, with the union saying the deal is below the true rate of inflation of 11.4%.

Full list of strike dates:

24 June
25 June
28 June
29 June
30 June

14 July
15 July
16 July
21 July
22 July
23 July
24 July
28 July
29 July
30 July
31 July

4 August
5 August
6 August
7 August
11 August
12 August
13 August
14 August
18 August
19 August
20 August
24 August
25 August
26 August
27 August