The air mass the plane is flying in changes, a normal process when crossing a jet stream or when there is turbulence in the air mass, like mountain waves or frontal passage.
Contrails are confined to narrow bands of altitude, always changing with the moving pressure systems. Weather briefings for fighter pilots always include the contrail altitude so they can be avoided denying detection to adversaries.
The grid patterns are because the planes are following established air routes. The air mass is always on the move, so that when the next airplane comes down that route, the original contrail has translated with the moving air mass. Several airplanes later and you have a set of parallel contrails.
Where there are two crossing airways, you get a grid patterns.
Now you’re making too much sense explaining contrails and the grid pattern. It seems many people are looking to find some grand conspiracy and won’t let anything interfere with their conclusions even as they are asking for explanations.
The funny thing is the military has done everything the can to ELIMINATE contrails.