https://en.wikipedia.org/wiki/Flying_Tigers
The first batch, some 300 men, departed San Francisco on 10 July 1941 and arrived in Rangoon, Burma on 28 July, via the Dutch ship Jaegersfontaine, operated by Java-Pacific Lijn. The second batch, some 30 pilots, departed on 24 September 1941 and arrived on 12 November 1941 via the Dutch ship Boschfontein. These volunteers used civilian passports in these trips.