I was astonished to read that experiments were conducted with a Convair B-36 strategic bomber landing and taking off on a tracked undercarriage. This was tried because the very heavy bomber broke through several concrete runways with its original single-wheel main undercarriage, which concentrated its massive weight (for the day) on a single point per side. As the National Museum of the USAF reports:
When the XB-36 was designed during World War II, specifications called for two main landing gear wheels to be equipped with the largest aircraft tires produced in the United States to that time. Manufactured by Goodyear, the tires were 110 inches in diameter and 36 inches in width. Weighing 1,320 pounds, each tire was 30 percent nylon cord construction, the equivalent of approximately 60 automobile tires or 12,700 pairs of nylon hose.
Because of the enormous pressures imposed by the XB-36 upon concrete runways when equipped with single wheels, it could takeoff and land safely at only three airfields (the Convair field at Fort Worth, Texas, Eglin and Fairfield-Suisun Army Air Fields). As a result, the single-wheel landing gear was redesigned and production B-36s incorporated four smaller wheels and tires on each of its main landing gears.
There's more at the link. It was hoped that a tracked undercarriage would spread the weight more evenly, and also permit operation from semi-prepared landing strips. You can read more about it here.
The system was first tested on March 29th, 1950. Here's (silent) footage of the tests.
What surprises me is how they were able to make a tracked undercarriage unit that could withstand the strain of accelerating its track from a standstill to the B-36's landing speed of over a hundred miles per hour, without shedding its track or suffering internal damage. That must have been a very robust track unit indeed!
Tracked undercarriage was also tested on other contemporary aircraft. You can see pictures of them at the link.