I'd phone up in advance to let the airline know your coming. Last time I flew "the worlds greatest airline" to the States, the Marker was no problem, but the Air Tank caused all sorts of problems.
After speaking to 3 people on the phone the week before including the head of security, the tank was allowed but must be open (as previously stated). Once at Heathrow the same procedure was repeated. It was only once we had gone through playing jerseys, slider shorts and copies of PGI etc that they realised I may in fact play Pball as a sport.
interesting though i got stopped at the plane door going out of Heathrow and Going out of JFK, for the old magic wand and shoes off b*llock feel up!!! - ahhhh, the pleasures of business class!!!