T4 has been closed for more than two years due to the Covid-19 pandemic.
The airport said that it has used this time to renovate the terminal, including its hold baggage screening machines, air conditioning and toilets.
Resumption of T4’s operations will create additional room in terminals 2, 3 and 5 before the summer rush, offering airlines more check-in space and stand capacity.
Passengers at T4 will have access to several retail, food and beverage outlets, and as airline occupancy grows over the summer, more outlets are planned to open.
To handle potential queues at check-in, Heathrow has expanded its customer service team and strengthened its ‘Here to Help’ team, which will mobilise head office employees, including senior managers, across terminals to assist travellers.
In addition to its customer service teams, the airport will appoint up to 1,000 new security officers and other airport staff, as well as support airlines and ground handlers in their hiring initiatives.
Heathrow CEO John Holland-Kaye said: “While we are still years away from passenger numbers returning to pre-pandemic levels, reopening T4 will give airlines at Heathrow extra space across the airport, helping them manage the impact additional travel documents continue to have on check-in times.
Qatar Airways will be the first airline to fly to and from T4 after it resumes operations.
It will be followed by nearly 30 carriers in July, including Kuwait Airways, Omanair, Royal Air Maroc, Gulf Air, Etihad Airways, Saudi Arabia Airlines and El Al Israeli Airlines.
Upon reopening, the terminal will be served by buses as well as Piccadilly Line and Elizabeth Line underground services. An inter-terminal transfer service will also be in place.