Any decent alternatives that one can use for keeping track of stats and that allow import from
appintheair?

flighty is planning an import feature but doesn’t have one yet. I never used flighty.

tripit will import your flights if you email them and pay for their subscription, but I never liked their interface.

I found a script on github that converts the aita data.txt file into something that myflightradar24 can read. While I use flightradar24 frequently for tracking aircraft, I never tried it as a tool to keep flight stats (and never saw it anywhere advertised either).