President Barack Obama spoke with 10 astronauts and cosmonauts on the International Space Station in a phone conversation Friday, offering his gratitude to those who have helped fly 135 shuttle missions in the past 30 years, USA Today reported.

I know that there have been thousands who have poured their hearts and souls into American's space shuttle program over the last three decades that are following this journey with special interest, Obama said. To them and all the men and women of NASA, I want to say thank you. You helped our country lead the space age and you continue to inspire us.

The Atlantis crew is leaving an American flag on the station that was flown on the first shuttle mission in April 1981. It will be turned over to members of the first crew to arrive at the station on a commercial spacecraft.

I understand it's going to be sort of like a capture the flag moment here for commercial spaceflight, the president said. So good luck to whoever grabs that flag.

That's an excellent point, sir, said Atlantis commander Chris Ferguson. We sure hope to see some of our commercial partners climbing on board really soon.

The call was the president's fourth to a shuttle crew in orbit, and it came on the 36th anniversary of the Apollo-Soyuz Test Project, the first cooperative space mission between the U.S. and Soviet Union.

It's pretty exciting to know that American astronauts and Russian cosmonauts aren't just shaking hands 36 years late, but are working every day with partners from other nations to represent humankind coming together in space, Obama said.

Obama began the phone call from the Oval Office by joking that he was trying to order a pizza and was surprised to find his call answered in space.

While this mission marks the final flight of the space shuttle program, it also ushers in an exciting new era to push the frontiers of space exploration and human spaceflight, Obama said in closing.