In 1927, while the airport was being fitted up in Saint-Hubert, a number of experiments were being conducted from a seaplane base near Rimouski, on the lower St. Lawrence River. To save precious time over the slow-going ships, mail was transferred from incoming and outgoing ocean vessels onto a waiting seaplane, and was then flown to the Montreal harbour front. The first successful exchange of mail from steamship to airplane took place on September 16, 1927, when 37 bags were flown to Montreal. In general, however, the experiments were fraught with difficulties: flights were often delayed due to thick fog and inclement weather. On one occasion, conditions were so bad that the mail had to be put on board the Montreal train!
Experimental flights were also carried out between Montreal and the Maritime provinces. On one cold December day in 1927, the air force pilot en route from Saint John, New Brunswick to Montreal was stranded by blowing snow and ice at Lac Mégantic near the U.S. border. He wired officials in Ottawa, "LANDED MÉGANTIC THURSDAY NIGHT STOP SNOW AND VERY STRONG WIND STOP MACHINE COVERED WITH ICE AND CARBURETOR FROZEN UP." He stayed there for several days before finishing his journey at a point north of Montreal, more than a hundred kilometres off course.