KABUL, Afghanistan — When Air Force Lt. Col. Michael Morales deployed here this year, he knew his job advising Afghan military pilots would be complex. But it has included an additional wrinkle, he said: Advocating on behalf of pilots as they fly more missions and face increasing demands from Afghan commanders.

The friction often comes when an Afghan general demands that a plane respond to his needs with little notice, Morales said. In a fledgling air force that has just four C-130 cargo planes and a couple dozen smaller planes, that’s a significant concern considering the number of missions and the routine maintenance the aircraft require. The generals have been known to threaten rank-and-file Afghan pilots with demotions in rank if they don’t respond quickly, Morales said.

“I would argue that there are a lot of things they could forecast with some planning,” Morales said of the Afghan commanders. “It’s our job to almost protect [the pilots] from the system until the system catches up.”

The tug-of-war is part of life while building the Afghan air force as the United States moves into its 15th year of military operations in Afghanistan. NATO Secretary General Jens Stoltenberg said Tuesday at a meeting of foreign ministers in Brussels that the military alliance will extend its funding of the Afghan government at a rate of $4 billion annually through 2020. It’s unclear exactly how that money will be spent.

The number of aviation missions the Afghan military has flown this year has climbed dramatically from 2014, as the force faces increasing demand and limited resources because the U.S. military has pulled back on how much help it offers through the air.

“My real bottom line is they have very good capability right now, they just don’t have enough of it,” said Air Force Brig. Gen. Christopher E. Craige, a fighter pilot who leads Train Advise Assist Command-Air, the U.S. unit that oversees air force training. “When you have a fight going on up in the north, and you have a fight going on in the east, and a fight going on in the west, and I don’t have enough airplanes, then I have to start making tough choices.”

With three months left in 2015, the Afghan air force already had flown 441 sorties with C-130s this year, or 47 percent more than the 299 flown in all of 2014, according to statistics released by Air Force advisers. The increase is prompted in large part by the United States delivering Afghanistan’s fourth C-130 in June 2015. The first C-130 flight flown exclusively by Afghans took off in June 2014, but many of them still include coalition advisers, due to the small number of Afghan pilots and navigators ready to fly.

The number of sorties by the MD-530 Warrior — a two-man attack helicopter with similarities to the Kiowa Warrior aircraft that the U.S. Army used for decades — also has increased this year, with 904 missions completed through September. That’s 18 percent more than the 765 that was flown in all of 2014, and includes the first missions flown in combat, beginning this August.

The Afghans also have relied more this year on aging Russian-made helicopters that U.S. advisers had recommended phasing out. Through the end of September, Afghan pilots flew 13,342 sorties in Mi-17 transport helicopters this year. That’s up from 4,544 in all of 2014, a 194 percent increase with three months to go in 2015. Afghan sorties with the iconic Russian-made Mi-35 attack helicopter also have skyrocketed this year, from 135 in 2014 to 893 in 2015 through the end of September. That’s a 561 percent increase with a quarter of the year remaining, though only one Mi-35 now remains in service.

Craige said the use of Russian helicopters — and the Afghan government’s interest in obtaining more — has complicated the U.S. advising mission. But the United States recognizes Kabul’s right to buy more of them if it wants, and will work with them if that occurs, he added.

Some Afghan commanders have been critical of the U.S.-bought aircraft. In an interview with The New York Times in September, for example, an Afghan colonel called the M5-530 helicopter a “total mess” that couldn’t effectively maneuver around and through Afghanistan’s mountain ranges. He also assessed that the C-208 — a 12-seat transport plane the United States has bought for Afghanistan — was “unacceptable to the geography of the country” because it can’t operate at high altitudes.

U.S. advisers dispute that argument. The aircraft provided were selected because they have a track record for being easy and affordable to maintain, they said. The C-208, for example, is based on a Cessna plane that has been used extensively in austere environments like Africa, Morales said. The Afghan air force now typically flies three C-208s per day out of Kabul, often to recover the remains of fallen soldiers, he added. One of the C-208s crashed in central Afghanistan in October.

American units also flew the Kiowa Warrior helicopter that has similarities to the MD-530 in Afghanistan for years. It had enough success there that when the Army decided in late 2013 to retire the aircraft, the decision was met with a groundswell of opposition from some of its pilots and ground troops who have been supported by it.

“You look at this capability that gives you rockets, guns and a bombing capability and it will more than make up for the Mi-35,” Craige said of the aircraft the Afghans will eventually field. “But the Mi-35 is definitely a cultural icon, is the bottom line. You will see that tension sometimes between [the Afghan] pilots, where the older pilots are like, ‘No, no, no. Nothing will work unless I have an Mi-35.’ And the younger pilots who are running around there are like, ‘This is great. This is awesome. We can use this.’”

Air Force Lt. Col. James Abbott, a former Kiowa Warrior pilot in the Army now advising the Afghans, said the demand for the MD-530 has become “insatiable” this year, especially after it completed its first combat missions this summer. It is now based not just in Kabul, but bases like Shorab, an Afghan-run airfield in Helmand province that was known as Camp Bastion until the coalition turned over control of it last year.

“This thing is like a high-performance race car,” Abbott said this fall during an interview in a Kabul aircraft hangar. “And nothing in aviation is cheap, but this is relatively cheap to fly.”

In its next big step, the Afghan air force is expected to begin receiving the A-29 Super Tucano from the United States in the next few weeks. Afghan pilots have been training with the turboprop aircraft at Moody Air Force Base in Georgia since last year. The Afghan air force is expected to eventually have 20 of them to carry out airstrikes.