They're really on EARTH!
They traveled away from the alien invasion but TIM, the android, couldn't find a habitable planet so he decided to have the ship go back to Earth before they reached their maximum amount of time in cryo-sleep knowing they would arrive back in the future. He reveals that he didn't tell the survivors where they were to prevent them from losing hope as it is programming to protect humans.
Little longer Pooper:
Earth is being attacked by aliens. We see them blowing up buildings and then see Lt. Frank Baum (Adrian Paul) wanting to stay and defend earth with his unit -- they are picked up by Captain Sam Crowe (Richard Grieco) and made to leave the earth on his rescue ship. They're all put into stasis and wake up as their ship is crash onto a lush earth-ish planet. As it turns out, they crashed into a lab where another ship's passengers were being held and studied by invisible creatures and they killed a bunch of them except for a few who argue with them and then join them after fighting off some of the invisible critters.
They rescue a girl from big bugs and the girl has camouflage body paint and is named Lea. She tells them she learned English by observing the people in the lab. She helps them down a river area and to an intact rescue ship. The android TIM distracts a large lizard away from it and upon inspection, the weapons are missing, the food is still there but is yucky, and the power cell - though it's not supposed to lose power for a thousand years - is drained.
She takes them to her people - who are not camo like she is, but are pasty white - and they enlist them to help in recovering a battery from their crashed ship to take back to the rescue ship to power it up. Everybody but Lea, TIM, Frank and Sam die to get the battery there and once they get into orbit, they find that they're on EARTH!
TIM explains that they were headed out to another planet but then, it turned out it wasn't habitable so they tried another, etc. but couldn't find another so he had the ship go back to Earth and, since they were traveling near the speed of light, a hundred years passed for them while 300,000+ passed for the Earth and Lea is the next step in human evolution. He didn't reveal this to them in order to give them hope.
Oh, and Frank and Lea have been smoochy-smoochying here and there and now that they know she's human it's cool so they have a little smooch on the rescue ship and then Captain Sam, Frank, and Lea decide to help free Earth from the occupying aliens.