"Q33 NY" refers to an Internet hoax which was spread, often via e-mail, in the wake of the September 11, 2001 attacks. The hoax capitalizes on an oddity of the Wingdings symbol font.
The message claimed that "Q33 NY," the supposed "flight number" of one of the airplanes to hit the World Trade Center, becomes a message when rendered in Wingdings font. In Wingdings, "Q33 NY" renders as:
(Note the skull and crossbones and Star of David on the right.) However, "Q33 NY" is not an actual flight number or an aircraft registration number - it's a meaningless assemblage of letters and numbers designed to take advantage of the font's symbols to infer a connection (prophetic or conspiratory) between the 9-11 attacks and Jews.
The actual flight designations of the airplanes striking the World Trade Center were American Airlines Flight 11 (so, AA11, first plane) and United Airlines Flight 175 (UA175, second plane). It is worth noting that in New York, there is a bus route Q33 serving LaGuardia Airport, which was not connected with any of the flights used in the attacks.