1.) flight/event cancelled. Probably after start up but before takeoff. Weather, maintenence, etc.
2.) The "merge" is where a fight starts when talking classic dog fighting. Basically pointed at each other, as soon as we pass, that is the merge and fights on.
"Making it to the merge" means you probably started out beyond visual range, and you are trying to survive BVR shots/tactics so you can make the merge. Duck and dive, so you can get in close and punch him in the face.