It’s a tough call. The good news is that whatever you decide, it will feel like the right thing after you’ve done it. You’ll almost certainly say to yourself, “I’m so glad we saw both islands” or “I’m so glad we had 6 full days on Santorini.” In deciding I would ask whether a return trip to Greece is likely or possible in the next couple of years. If so, then spend your 6 days on Santorini and explore that island, then return to Crete at some time in the future for a deserving 7 to 10 days. But if this is a one-time deal for the foreseeable future then do 3 days on Santorini and 3 days in Crete. (Whatever you decide don’t do a day trip to the other island as it’s not worth the time and effort.)
With the outbreak of World War II, the airline presence in Asia came to a relative halt, with many new flag carriers donating their aircraft for military aid and other uses. Following the end of the war in 1945, regular commercial service was restored in India and Tata Airlines became a public limited company on July 29, 1946, under the name Air India. After the independence of India, 49% of the airline was acquired by the Government of India. In return, the airline was granted status to operate international services from India as the designated flag carrier under the name Air India International.