The hill doubled as an underground aircraft shelter.

Other: Air attacks have destroyed more than 70 hardened aircraft shelters.

The most significant remnants of the Vietnam War years are the concrete aircraft shelters, which have been abandoned since 1975.

Over the years the base was expanded, and a number of hardened aircraft shelters built.

Iraq had invested billions in the construction of nearly five hundred hardened aircraft shelters.

He saw a hardened aircraft shelter which had escaped damage so far.

Additionally, bombs were used to destroy several hardened aircraft shelters.

It had four hardened areas-one each on either end of the main runways-with approximately 30 individual aircraft shelters.

An armored vehicle had pulled out in front of them from one of the small aircraft shelters.

As many as 300 of Iraq's estimated 500 hardened aircraft shelters have been destroyed, the general said, and more would be targeted.