Through the Purple Cloud — Jack Williamson

From the early days of Pulp Science Fiction comes this tale from an SF Grand Master. George Cleland, while returning home on a small passenger plane with three other passengers, flew into a purple cloud that suddenly appeared out of nowhere. Passing through the cloud they plummet into the black mountains under a blood red sky. The purple cloud is a gateway into the fourth dimension that takes them to a weird and inhospitable world. George and his new friend and love interest, Juanita, have to survive on this strange world while encountering blood-red rain and a mad man!