RAF Typhoon FGR4 inside a lit hardened aircraft shelter at Gioia del Colle, Italy, at night in 2011

Hardened Aircraft Shelters: Why Air Forces Put Fighters in Concrete

by Joseph Duncan | Oct 4, 2026 | Military Aviation | 0 comments

A fighter jet is never more vulnerable than when it is parked. In the air it can manoeuvre, climb, jam and fire back. On the ground, with its pilot asleep and its tanks being filled, it is a very expensive target that cannot move. For most of the jet age, the answer has been to put it inside a mound of reinforced concrete.

The hardened aircraft shelter, usually shortened to HAS, is one of the least glamorous pieces of military aviation and one of the most important. Wars in Ukraine and the Middle East have pushed it back into the headlines. Here is why air forces build them, how they work, how they have been defeated, and why the debate over them is suddenly urgent.

Quick Facts

What it is: A reinforced concrete hangar for one or two combat aircraft, with heavy blast doors
Catalyst: Operation Focus, 5 June 1967: Israel destroys most of Egypt’s air force on the ground
NATO design standard: Survive a direct hit by a 500 lb bomb or a near miss by a larger one
Gulf War 1991: Coalition aircraft destroyed over half of Iraq’s shelters
Cost: About $4 million per single-aircraft USAF shelter in 1999; estimates of $5 million to $30 million today
Western Pacific: Since the early 2010s China has more than doubled its aircraft shelters to over 3,000; the US added two hardened shelters

The Morning That Changed Air Base Design

The modern hardened shelter was born from a single morning. On 5 June 1967, at the start of the Six-Day War, the Israeli Air Force launched Operation Focus against Egyptian airfields. The Egyptian Air Force had its aircraft parked in the open, and most of it was destroyed on the ground within hours.

Every air force in the world drew the same lesson. NATO and the Warsaw Pact went on to build hundreds of hardened shelters across Europe, and air forces in the Middle East, Asia and elsewhere followed. An aircraft that cannot be destroyed on the ground forces an enemy to fight it in the air.

Perun on hardening, modern threats and air base defence.

How a Hardened Aircraft Shelter Works

A typical HAS is a reinforced concrete arch, often covered with earth, just large enough for one or two fighters. The front is closed by massive sliding or hinged blast doors, and many designs include a separate exhaust port at the rear so that an aircraft can run its engines inside.

NATO shelters of the Cold War were designed to withstand a direct hit by a 500 lb bomb, or a near miss by a larger one of 1,000 lb or more. The shelter protects against blast and fragments, but just as importantly it hides what is inside. An enemy looking at a row of closed doors cannot tell which shelters hold aircraft and which are empty.

Green-painted hardened aircraft shelter with closed blast doors at Leeuwarden Air Base in the Netherlands — A hardened aircraft shelter at Leeuwarden Air Base in the Netherlands, with its blast doors closed. Photo: Hnapel, Wikimedia Commons, CC BY-SA 4.0

Shelters like this one at Leeuwarden Air Base, home to F-35s of the Royal Netherlands Air and Space Force, are still in daily use. The Royal Air Force operated Eurofighter Typhoon fighters from hardened shelters at Gioia del Colle in Italy during the 2011 Libya campaign, as in the photo at the top of this article.

AiirSource Military footage of a hardened aircraft shelter door opening.

1991: When Precision Bombs Beat Concrete

The Gulf War showed that hardened shelters could be defeated. Iraq had built some of the strongest shelters in the world, and early in the air campaign many Iraqi aircraft sat inside them. Coalition air forces developed tactics to break them open, first using a TV-guided missile to blast the doors and then bombs aimed at the opening, and later dropping a 2,000 lb laser-guided bomb straight through the roof.

By the end of the war the Coalition had destroyed over half of Iraq’s hardened shelters. The lesson was that a shelter buys time and forces an attacker to spend precision weapons, but it does not make an aircraft invulnerable.

Two concrete hardened aircraft shelters with bomb damage at Al-Salman Air Base in Iraq after Operation Desert Storm — Bomb-damaged hardened aircraft shelters at Al-Salman Air Base, Iraq, after Operation Desert Storm in 1991. US Department of Defense photo, public domain

Ukraine: Bombers Parked in the Open

The war in Ukraine has shown the opposite problem: what happens to aircraft that are not sheltered at all. On 1 June 2025, in Operation Spiderweb, Ukraine launched small drones from trucks parked near Russian air bases, some of them thousands of kilometres from the front. Strategic bombers such as the Tu-95 and Tu-160 were parked in the open.

Ukraine’s Security Service claimed 41 aircraft were hit. US officials estimated that about 20 were hit and about 10 destroyed. Russia moved many of its bombers to more remote bases and has expanded hardened shelters at its airfields under repeated Ukrainian drone and missile attacks.

2026: The Cost of Leaving Aircraft Outside

The 2026 Iran war brought the same issue to American bases. Iran fired ballistic missiles and drones at US air bases in the region, and on 27 March 2026, according to Military Times, an Iranian missile struck Prince Sultan Air Base in Saudi Arabia and destroyed a US Air Force E-3 AWACS that was parked on the open ramp.

“What on earth was this half-billion dollar airplane doing sitting right out in the open?”

Tom Shugart — Retired US Navy officer, Center for a New American Security, speaking to Military Times

Military Times reported that the Pentagon issued solicitations in March 2026 for bunkers and other base infrastructure, including prefabricated transportable bunkers. It also cited expert estimates that a single hardened aircraft shelter costs about $5 million to $30 million, a fraction of the value of the aircraft it protects.

The Concrete Gap in the Pacific

The sharpest version of the debate concerns the western Pacific. In January 2025 the Hudson Institute published Concrete Sky: Air Base Hardening in the Western Pacific, by Timothy Walton and Thomas Shugart. It found that since the early 2010s China had more than doubled its hardened and unhardened aircraft shelters to more than 3,000, while the US military had added two hardened shelters and 41 unhardened ones in the region.

“China now has 134 air bases within 1,000 nautical miles of the Taiwan Strait — airfields that boast more than 650 HASs and almost 2,000 non-hardened IASs.”

Timothy Walton and Thomas Shugart — Concrete Sky, Hudson Institute, January 2025

Supporters of hardening argue that concrete is cheap compared with the aircraft it saves. Others argue that money is better spent on dispersal, airfield repair and air defence. Most analysts agree that the answer is some mix of all of them, and that the fighter parked in the open is the easiest target in any war.

The Wall Street Journal on how China is upgrading its air bases.

Sources: Wikipedia, Hardened aircraft shelter and Operation Spiderweb; Hudson Institute, Concrete Sky: Air Base Hardening in the Western Pacific, January 2025, as reported by The War Zone; Military Times, 6 April 2026; UK Ministry of Defence and US Department of Defense photo captions

Frequently Asked Questions

What is a hardened aircraft shelter?

A hardened aircraft shelter, or HAS, is a reinforced concrete hangar built to protect one or two combat aircraft from bombs, missiles and drones. It has heavy blast doors at the front and often an exhaust port at the rear. It also hides whether an aircraft is inside, which complicates an attacker’s targeting.

Why did air forces start building hardened aircraft shelters?

Air forces started building hardened aircraft shelters in large numbers after Operation Focus on 5 June 1967, when the Israeli Air Force destroyed most of the Egyptian Air Force on the ground in the opening hours of the Six-Day War. NATO and the Warsaw Pact then built hundreds of shelters across Europe.

Can a hardened aircraft shelter stop a bomb?

A hardened aircraft shelter can stop some bombs but not all. NATO Cold War shelters were designed to survive a direct hit by a 500 lb bomb or a near miss by a larger one. In the 1991 Gulf War, Coalition aircraft used 2,000 lb laser-guided bombs and destroyed over half of Iraq’s shelters.

How much does a hardened aircraft shelter cost?

In 1999 a hardened shelter for a single aircraft would have cost the US Air Force about $4 million. In 2026 Military Times cited expert estimates of about $5 million to $30 million per shelter, which is a small fraction of the value of a modern combat aircraft or a large support aircraft.

How many hardened aircraft shelters does China have?

According to the Hudson Institute report Concrete Sky, published in January 2025, China has more than doubled its aircraft shelters since the early 2010s to over 3,000. Its 134 air bases within 1,000 nautical miles of the Taiwan Strait have more than 650 hardened and almost 2,000 non-hardened shelters.

Were the Russian bombers hit in Operation Spiderweb in shelters?

No. The Russian strategic bombers attacked by Ukrainian drones in Operation Spiderweb on 1 June 2025 were parked in the open. Ukraine claimed 41 aircraft were hit, while US officials estimated about 20 were hit and about 10 destroyed. Russia later moved bombers to more remote bases.