ISLAMABAD (AP) — Over a dozen Pakistani air force planes have crashed in roughly the past 18 months, raising concerns about the health of an aging fleet that officials are struggling to upgrade because of a lack of funds.

A significant number of the air force’s combat aircraft are nearly half a century old and have been called on in recent years to help the army fight a domestic Taliban insurgency that has killed thousands of people. This has added to the strain on a force that has historically focused on countering the threat from Pakistan’s neighbor and archenemy, India.