The Pentagon will significantly expand the number of daily drone sorties conducted around the globe during the next several years and will for the first time expand the mission beyond the Air Force, a defense official said.

The plan reflects a high-level recognition that the Air Force's remotely piloted vehicle fleet can no longer meet the forcewide demand for combat air patrols flown by drone pilots, mainly due to severe pilot shortages.

"Demand exceeds supply in this type of mission," Navy Capt. Jeff Davis, a Pentagon spokesman, said Monday.

The new plan aims to ratchet up the number of daily drone flights from the current level of about 60 each day to 90 by 2019, a goal that will affect long-term planning for budgets and manpower, Davis said.

The Air Force's drone fleet will maintain its current requirement of 60 daily combat air patrols, Davis said. The Army will assume responsibility for between 10 and 20 daily sorties; U.S. Special Operations Command will provide 10 drone flights per day; and contractors will handle up to 10 additional flights, Davis said.

Any sorties conducted by contractors would have to be unarmed, Davis said.

Last year, the Defense Department tried to reduce the number of combat air patrols that Air Force drone pilots fly to 55 per day as the U.S. mission in Afghanistan wound down. But after the Islamic State group conquered large parts of Iraq, the need for drones soared and the U.S. began daily intelligence, surveillance and reconnaissance missions over Iraq and Syria.

The increase is expected to will affect manpower requirements.

"As we talk about expanding UAV flights, we also have to look at the workload of the analysts that process those," Davis said. The plan is "meant to inform budget requirements, [and] inform how we man, train and equip the force."

The plan will expand use of the Army's growing fleet of MQ-1 Gray Grey Eagles, a variant of the Air Force's Predator. The plan also hands the Army an expanded high-profile mission at a time when budget cuts are forcing trims to the ground combat force.

The Navy does not have a significant fleet of large unmanned surveillance aircraft. The Navy MQ-4C developed under the Broad Area Maritime Surveillance program is not expected to be operational until 2017.

The Air Force has struggled to retain pilots for its fleet of remotely piloted aircraft. The reasons include long work hours driven by global demand, lucrative alternatives in the private sector and long-standing complaints that the Air Force treats them like second-class pilots compared to the manned-aircraft pilots that dominate the service's leadership.

The Air Force announced in July that MQ-1 Predator and MQ-9 Reaper drone pilots will be eligible for retention bonuses worth up to $135,000 beginning next year.

The Air Force estimates it needs to train 300 drone pilots per year to keep up with demands, but the training pipeline's capacity can handle only about 180, Air Force officials said.

A recent Government Accountability Office report found that the Air Force had 83 percent of the drone pilots it needs as of March. The report also found that only 35 percent of unmanned aircraft pilots had trained for all of the seven missions they are expected to fly due to pilot shortages and the relentless demand for sorties around the world.