Right up until the 1960s the most common form of transportation by NHL teams to get to road games was the train.
It was not so bad as it may sound nowadays. It was cost effective. Plus the Original Six teams are more or less in a geographical cluster of North America. Montreal, Toronto, New York, Boston and Detroit are all a few hours apart. Only Chicago was considered a real long trip.
But teams started spending money on air transportation as the mode of travel became more economic and common. Flying became common in the 1960s, and was even increasingly used in the 1950s.
But it was actually way back in 1935 that the first NHL team chose to travel by air. New York Rangers president Colonel John Hammond decided the easiest way to the Rangers to Toronto and back would be by air. He booked a flight with the Curtis-Wright Corporation and packed up Frank Boucher, Bill and Bun Cook and the rest of the Rangers.
The Rangers did not fare too well in the game. They lost the game 6-5 to the Toronto Maple Leafs.
Given all of the air travel by NHL teams nowadays, it is amazing we don't have more close calls than we do. I remember in recent years that the Detroit Red Wings and Vancouver Canucks had scares while traveling.
In 1948 a plane carrying some members of the Czechoslovakian national team for exhibition games in London, England. Eight players went on one flight, while six went on the second and doomed flight. The plane went missing over the English Channel, killing Slovak hockey legend Ladislav Trojak and teammates Zdenek Jarkovsky, Miroslav Pokorny, Vilibard Stovik, Zdenek Svarc and Karel Stibor. The plane was never found.