The Yardbollenko-Majorov S-300 is a Bohemian superheavy (according to the Bohemian classification of the mid-40s) wide-body long-range flying boat aircraft, created in collaboration with the Yardbollenko Design Bureau and the Mayorov Design Bureau. The aircraft was designed to serve Guild Air's long-range and ultra-long-range routes of over 7,000 km.
It was the first aircraft in the history of Bohemian aviation to be developed by several design bureaus at once.
It was assumed that this type of aircraft would make regular flights to the cities of the New World, in particular, it was the S-300 that was supposed to serve the route between the capital of Bohemia, St. Waalburg and New Amsterdam. It was also supposed to be used on the Waalburg-Tokyo route, which was the most popular long-distance route operated by Guild Air.
However, due to the excessive cost and bulkiness, the construction of the aircraft was stopped. To replace it, a less majestic, but much more practical and easy-to-produce YB-49 was created, which went into operation.