The Air Force Academy’s Class of 2015 was warned Thursday about the dangerous and uncertain world it will face as officers.

Graduation speaker Air Force Secretary Deborah Lee James told the 840 graduates that they will be asked to sacrifice, fight and possibly give their lives for the country that sent them to college.

“This pace of operations is not likely to lessen. It is likely to be with us for the foreseeable future,” James said.

That didn’t faze the new lieutenants.

“It’s the best day of my life,” said newly minted 2nd Lt. Zachary Modly, 23, of Annapolis, Md., as he enjoyed the Thunderbirds air show after getting his diploma.

Despite the crash of an Air Force Thunderbirds after its flight over Falcon Stadium, the grads said it was a great day for a graduation. Rainstorms that threatened the rite came after the ceremony and air show were over. Tight security didn’t tangle traffic as badly as expected, and the timing of the hat toss perfectly meshed with the arrival of the Thunderbirds flying team over Falcon Stadium. And the pilot of the jet that crashed ejected safely.

“It’s one of the best feelings I’ve ever experienced,” said 2nd Lt. Michelle Ferguson of Lakeville, Minn.

The great feeling came after a long four years. The class started at the school with 1,137 freshmen, but four years of grueling academics and tough discipline at the Air Force Academy took a toll. More than a quarter of the class didn’t make it to graduation.

During its years at the academy, the class watched as the Pentagon slashed its budget, downsized the Air Force, and furloughed civilian workers, including professors at the school. Dyrung their time at the academy, the Air Force also accepted gay soldiers openly into its ranks and saw the Iraq War end and begin anew as a battle against the Islamic State terror group.

“It’s a little nerve-wracking, especially with the way the world is,” said Michelle Wong, who flew in from Boston to watch her brother Jacob graduate with the goal of flying. “It’s his dream, so we can be nervous but (we) just have to support him.”

James said the graduates need to thank family members for helping through the tough times.

“None of you would be here today without the unwavering support they have given you throughout your entire lives,” she said.

In her speech, James told cadets the story of Zebulon Pike, the officer that found the mountain that towers over the region.

Pike never climbed Pikes Peak. He feared that reaching the summit was impossible, she said.

“All of you are far better prepared than Zebulon Pike was,” James said.

The secretary said the Class of 2015 is one of the best groups in the Air Force’s history. It’s also the most diverse to graduate from the academy, with one female cadet for every four males.

James said cadets will join an Air Force that is increasingly concerned with Russian aggression, dealing with the technological rise of potential foes and still struggling with fiscal austerity.

“I charge you to lead us into the future where you will need to confront and overcome challenges unlike anything you’ve ever imagined,” she said.