Commander Aircraft is apparently the latest casualty of 9/11 and the generally weak aviation market. The Bethany, Okla., plane-maker has asked a bankruptcy judge to convert its bankruptcy case from a Chapter 11 reorganization to a Chapter 7 liquidation. The company built about 200 of the speedy and luxurious four-place singles between 1992 and 2002. It was hit hard by recent downturn and attempts at attracting new capital apparently failed. Precipitating the most recent turn of events, an investor who had planned to sink $2.8 million into the company for an 80-percent share a couple of weeks ago defaulted and forfeited his $200,000 deposit. Before that, another potential investor walked away from his $800,000 deposit rather than carry through with his investment. Commander Aircraft bought the piston single line from Gulfstream Aerospace in 1988 and obtained a new type certificate for its modernized version of the aircraft, which was originally developed by Rockwell.