Throughout the 1930s, all bush plane companies operated with very low margins, and had very few customers. So when the Second World War began, many men who had been working in the bush left to join the effort. Many mills also closed, leaving still fewer customers for bush pilots.

At the same time, these small aviation companies could not procure new aircraft or parts, since aircraft manufacturers had shifted their focus to producing aircraft for the war effort. Fuel and supplies were regulated and bush pilots had to obtain permission to receive a share.

These factors had a massive impact on the industry and many companies faced bankruptcy.

In 1937 McConachie’s company, United Air Transport, supplied regular transport services and airmail to the Grande Prairie and Peace River regions. That same year he increased his services, flying between Edmonton and Whitehorse once a week with stops in Grande Prairie, Fort St. John, Fort Nelson, and Lower Post on the British Columbia and Yukon border. When McConachie expanded his service he renamed his company Yukon Southern Air Transport.

Yukon Southern Air Transport was among the strongest bush plane companies, so much so that when the Japanese bombed Pearl Harbour and the Americans feared the possibility of the Japanese landing in Alaska, McConachie’s company was considered vital to national security. He had the aircraft and the expertise to transport personnel and equipment north to where the Americans wanted to build airfields and the Alaska Highway.

Even with this increased activity, Yukon Southern Air Transport had too much debt, so when an offer came to sell the airline to Canadian Pacific Air Lines (CPA), McConachie accepted.