Can DVT show up several days after an airplane flight?

Yes. One can form a clot after a plane ride and then not notice it for several days. This depends on several factors. Swelling , pain, heat and redness are signs of a dvt. Plane trips are a know risk for developing dvt.
DVT timeframe. DVT typically shows itself within 2 weeks of the causal event. It can occur within several days (of flying or surgery for example) or even as long as 2 to 3 weeks post the initiating event. If suspicious of a DVT then a venous duplex exam of the area should be done as the initiating diagnostic test.