He was aboard during the ship's first mission, and took part in the Battle of Atlantis. During the battle he served as the weapons officer and controlled the Asgard transporters. After twelve more Hive Ships were detected heading toward Atlantis, he traveled with the Daedalus to the spot where they would exit hyperspace. They destroyed another two Hive Ships, but the Wraith developed countermeasures preventing beaming of nukes onto their ships. Colonel Steven Caldwell then ordered them to enter hyperspace but not before sustaining damage. (SGA: "The Siege, Part 3")
When Michael Kenmore returned to Atlantis with his Hive Ship to form an alliance with the Atlantis expedition, he and the Daedalus were sent on a mission to test the effectiveness of the Iratus bug retrovirus on a Hive Ship. When the exited hyperspace, they were immediately fired upon by both Hives. The Hives then entered hyperspace. He returned to Atlantis and was informed they were on their way to Earth. (SGA: "Allies")
The Daedalus was then dispatched to intercept the Hive ships on their way to Earth, Colonel Steven Caldwell specifically instructed Kleinman to configure all of the Daedalus's missiles to launch as soon as the ship exited hyperspace, a task that he doubted was possible, but nonetheless managed to accomplish. He was also involved in repairing the life support after the battle. He then traveled back to Atlantis when the Hive towed the Daedalus through hyperspace. (SGA: "No Man's Land", "Misbegotten")
Later, during the first test of the McKay-Carter Intergalactic Gate Bridge he was piloting the Daedalus. During the test, the Tria went by and Colonel Steven Caldwell told him to follow them. Later on, after the Asurans' take over of Atlantis, he was piloting the Daedalus carrying a bomb to destroy Atlantis. When Atlantis made contact he informed Caldwell of the development and opened a channel to the city on his orders. He was then ordered to prepare a team of Marines to beam down to check out the team's story and Caldwell commented to him that he was sure they were going to get an interesting story. (SGA: "The Return, Part 1", "The Return, Part 2")
He was aboard the George Hammond when it was sent to the second Icarus type planet in an attempt to stop the Lucian Alliance from dialing the ninth chevron to Destiny. He monitored sensors during the attack and, as the planet became unstable, notified Colonel Samantha Carter that two F-302 fighter-interceptor's had not yet returned. Carter made the decision to leave the two behind. (SGU: "Incursion, Part 1")
- Kleinman's name has never been spoken on screen. Throughout Stargate: Atlantis, Colonel Steven Caldwell addresses him as "Weaps" (which is short for "Weapons") and he is credited as "Daedalus Tech" or "Airman." His appearance on Stargate Universe went uncredited; however, his name and rank have consistently been shown on his flight suit.
- He is the only character to appear in Stargate: Atlantis and Stargate Universe, but not in Stargate SG-1.