Direct an Internet browser to the FAA "Releasable Aircraft Data." Click the download database link. This is a large document and may take a few moments to download and occupy a bit of space on your hard drive.
Follow the database table of contents to the aircraft types. This helps you narrow the search. For instance, if you suspect the person owns a Cessna 182, go to the Single Engine section.
Read the database for either registration name (filed alphabetically with the last name first), or for the aircraft's registration identifier code. This is the series of letters and numbers found on the aircraft tail or rear fuselage. For example, an aircraft registration code looks something like "N34QP."