In a light airplane, my longest trip was a new airplane ferry ... Independence, KS to Memphis, TN to Atlanta, GA to Salisbury, NC in a Cessna 172. Eight plus hours flying, close to 1000 miles.
In my current job, my longest single day was Beaufort, NC to Winston-Salem, NC to Beaufort, NC to Teterboro, NJ to Rocky Mount, NC to Windsor Locks, CT. Another eight hour flying day, but a lot more miles covered.
FL270