Dr. Nick: It seems as if Sachiel has a jet engine up his arse.
Reichu: One of the more profound Sachi-related observations I've read. ;;>
felineki: This seems to be a method of “A.T. Field Propulsion”. If you look, you can see that there is a lot of force being pressed down against the ground, which would then propel Sachi upwards (equal but opposite reaction, such and such…). This particular “move” is used at least twice more in the series.
Reichu: The script here seems to imply that Sachiel takes his giant leap because he is surrounded by fighters and, presumably, wants to get out of that situation. My overall impression is that Sachiel (prior to the N² mine later, anyway) isn't interested in a fight; his actions are either reciprocal or avoidatory. He didn't take out all of the VTOLs even though he easily could,as he is apparently more interested in avoiding them.
Gundampilotspaz: He doesn't get truly violent until he reaches Tokyo-3. I'm sure if he wanted to, he could unfold his AT-Field here and just take those fighters out.