A study of the "Cope India" air exercise, conducted by the US and Indian air forces in Gwalior, India last February, is secret, said General Hal Hornburg, head of the air force's Air Combat Command.
"But we have to learn a lot of things from that," he told defense reporters here. "We have to learn if we want air superiority it doesn't come cheap and it's not automatic."
The Russian-made SU-30s are reported to have bested the F-15s in a majority of their engagements, much to the surprise of the organizers.
It was the first time the two top-of-the-line US and Russian-made fighters have flown against each other in an exercise, an air force spokeswoman said.
It pitted F-15Cs from the air force's 3rd Wing out of Elmendorf Air Force Base in Alaska against a variety of Indian fighters, not just the SU-30s. They included Russian-built MiG-21s, MiG-29s and French-made Mirage 2000s.
Although the US fighters flew with certain restrictions that handicapped their effectiveness, the performance of the Indian fighters exceeded expectations.
"In general, we may have learned some things that suggest we may not be as far ahead of the rest of the world as we once thought we were," Hornburg said.
He said the results of the exercise showed the need for the F/A-22 Raptor and the Joint Strike Fighter (JSF). Both aircraft are stealthier than the F-15, but the F/A-18 also has greater range and speed than the air force's existing fighters.
The air force has been battling the perception that the costly new fighters are a luxury at a time when the United States has dominance in the air.
"I thought it was a wake-up call for some things that we've been talking about before, and it provided validation," Hornburg said.
The trade journal Aviation Week and Space Technology reported last month that the exercises showed the SU-30s had a clear advantage over the F-15C in a long-range fight.
The US and Indian aircraft were seeing each other at the same time with their radars but the SU-30 pilots were able to simulate-fire their Russian-made AA-10 "fire-and-forget" Alamo missiles first, the weekly said.
Experts say the SU-30 has a more advanced radar than the F-15C.
Hornburg said the F-15Cs that took part in "Cope India" were not equipped with the latest US active electronically scanned array radar.
"We are going to put new radars, as much as we can afford, in the F-16s and the F-15Es, and my prediction is we will have to do for the F-15C as well in due course," the general said.
The exercise appears to hold lessons for the air force in east Asia, where China is acquiring SU-27 and SU-30 fighters and AA-12 air-to-air missiles.
"I see air forces across the spectrum and across the world becoming better and better as each year passes," Hornburg said.
"China is very formidable. It is a huge, collossal nation, and they are very technologically adept. Do I worry about the Chinese? I would say I worry about anyone who could be a possible threat, to include them and many others," he said.