Heathrow Terminal 4

Heathrow Terminal 4 is an airport terminal at Heathrow Airport, the main airport serving London, England, situated to the south of the southern runway, next to the cargo terminal. It is connected to Heathrow Terminals 2 and 3 by the vehicular Heathrow Cargo Tunnel, and by rail with the Heathrow Terminal 4 tube and Heathrow Terminal 4 railway stations.
The terminal was temporarily closed in 2020. 
Built at a cost of £200 million, Terminal 4 was opened by the Prince and Princess of Wales on 1 April 1986. British Airways was the main airline operating from the terminal from 1986 until its move to Terminal 5 on 29 October 2009, eventually making Terminal 4 the Heathrow base for airlines of the SkyTeam airline alliance.
Overview.
Terminal design.
The terminal was initially designed as a facility for short-haul 'point-to-point' traffic, to compensate for its relatively long distance from the airport's central terminal area (CTA). The layout of the terminal, with passenger boarding gates very close to the check-in and security halls, was designed to facilitate rapid movement of passengers through the building (a requirement for short-haul, business-focused flights). Upon opening, it boasted other innovations including the complete segregation of arriving and departing passengers and a departure concourse over long.
Lord King, then Chairman of British Airways, demanded that Terminal 4 be solely for the use of British Airways to fulfill the airline's ambition of hosting all its flights in one terminal (an ambition that still has not been achieved even with the opening of Terminal 5 in 2008). A similar demand was made on the North Terminal at Gatwick.
Terminal 4's distance from the CTA and design were ill-suited for British Airways' long-haul operations and could be seen as a contributor to the airline's dire operational performance, particularly in the years up to Terminal 5's opening in 2008. For example, passengers had to transfer between Terminal 4 and the CTA by bus rather than by a short moving walkway (as between Terminals 1 and 3 for example) and once inside Terminal 4, the gate areas are not large enough for the 400+ passengers waiting to board the waiting Boeing 747s. Passengers' baggage also had to make the trip by van, sometimes resulting in the luggage being mislaid, although this problem was somewhat alleviated in the late 1990s by the construction of an automated transfer tunnel between the CTA and Terminal 4.
Improvements and renovations.
Following the transfer of most of British Airways' flights to Terminal 5 during 2008, Terminal 4 underwent a £200m upgrade to enable it to accommodate 45 airlines and serve as the base for the SkyTeam airline alliance. The departures forecourt has been upgraded to reduce traffic congestion and improve security and an extended check-in area opened in late 2009. Most internal areas of the terminal were renovated between 2009 and 2014, whilst a new SkyTeam Alliance passenger lounge for premium passengers opened in 2009, more recently followed by the Etihad Airways Lounge. A Malaysia Airlines Golden Lounge, Gulf Air Golden Falcon Lounge, Qatar Airways Premium Lounge and Plaza Premium Lounge have all opened since 2010. Two new stands to accommodate the Airbus A380 were constructed in 2009, and a further two opened in 2015. A new baggage system has also been installed. Refurbishment of the arrivals areas is ongoing as of early 2016.
Closure during the COVID-19 pandemic.
In 2020, all flights from Terminal 4 were suspended as a result of the COVID-19 pandemic. Consequently, rail and tube services to Terminal 4 station were withdrawn; TfL Rail services were diverted to T5. Heathrow also closed one of its runways in response to the drop in flights.
Usage.
SkyTeam.
All SkyTeam members with operations at Heathrow fly from Terminal 4, with the exceptions of Middle East Airlines and Delta Air Lines which use Terminal 3. The latter vacated to Terminal 3 on 14 September 2016 to ease connections with partner Virgin Atlantic.
Oneworld.
Three Oneworld members fly out of Terminal 4, Malaysia Airlines, Royal Air Maroc and Qatar Airways. All have joined the alliance since moving to Terminal 4. Sri Lankan Airlines formerly operated from Terminal 4 but shortly after it joined Oneworld in 2014 it transferred its flights to Terminal 3.
Star Alliance.
No Star Alliance airlines currently have presence in Terminal 4. 
Previously, Air India moved its flights to Terminal 2 on 25 January 2017 after joining Star Alliance in 2014. United Airlines also previously operated from this terminal until it moved to Terminal 2 on 4 June 2014.
Non-aligned.
The principal non-aligned airlines are Etihad Airways, Royal Brunei Airlines, El Al, Gulf Air and Oman Air.
Ground transportation.
Road links.
Terminal 4 is accessed from Junction 14 of the M25 motorway via the A3113 and then the Southern Perimeter Road. It is also accessible from Central London via the M4, exiting at Junction 3. There is a short stay car park directly opposite the terminal and a long stay car park on the other side of the twin rivers.
Rail links.
Terminal 4 is served by Heathrow Terminal 4 Underground station on the London Underground's Piccadilly line and by Heathrow Express trains at Heathrow Terminal 4. Heathrow Express provides a free shuttle service to Heathrow Central station. At Heathrow Central, passengers can change for free services to Terminal 5, and also for the main Heathrow Express service to Paddington or the TfL Rail (formally Heathrow Connect) stopping service. As of February 2019, a standard adult single ticket to Paddington on Heathrow Express is £25.00 (£22.00 off-peak) if purchased before travel, or £27.00 if purchased on the train.
The Piccadilly line has up to six trains per hour (about every 10 minutes) in the direction of Cockfosters via central London. Trains to central London run via Heathrow Terminals 2 & 3. They may wait at Heathrow Terminal 4 for up to eight minutes. Although the journey takes longer, fares are much cheaper than on the Heathrow Express service. As of February 2019, adult single fares to central London stations range from £3.10 to £6.00, depending on the time of day and whether or not a contactless payment card (including the Oyster card or Tfl Oyster App) is used.
Bus links.
Terminal 4 is served by some local buses, coach services and car parking.