it is actually a three leaf clover and it is Are Lingus
Air Lingus (sp)
Morris County Golf Club in New Jersey http://www.morriscgc.com/
4H Club, France National Lottery
Trend
Yes It can. X pills that are mostly or completely white in color usually have cocaine in them, though.
It's not just Irish. It's actually pretty universal. For example, France use it as their national lottery logo.
Iberdrola has a logo with a green leaf and two drops.
Did you really mean "airplane" - or did you mean airline . -If airline it is Qantas.
Pan Am
You can see the Indigo airline emblem on it's wikipedia page here.
Ryanair
A Navy Flight Surgeon uses this very insignia. Airline, I do not know.
Salada