On Pan Am DC-3s in the early 1940s there were two pilots (the Captain and the First Officer), the radio officer and a stewardess.
The primary duty of a Flight Radio Officer was to provide air to ground CW comunications. A 2nd Class FCC Telegraph License was required. Before his first flight he was also required to take the Pan Am Dead Reckoning Navigation course and 8 hours of manual loop training in Stinson Voyager blind flyer.
The FRO would report for duty at field operations an hour before flight departure time, check in and then board the plane to ground check all the radio equipment. He would contact the local CW operator on CW and the local tower on voice and then setup the receiver and transmitter for the pilots to talk to the tower upon departure.
After departure the FRO would log the time of departure. The pilots would then turn radio comunicatians over to him. The FRO would contact the ground CW operator sending departure time, number of passengers aboard, weight & balance, fuel on board and ETA to destination. The FRO would maintain contact every 30 minutes and send position reports at least every hour. He would receive enroute weather and keep in touch with other planes in the area.
Before the days of automatic direction finders the FRO would give the pilots relative bearings to their destination using a manual loop antenna or, if bad weather, to stations along the route. From these we could determine our position. When flying to central America during bad weather we would often have to overhead the station and then do a let down pattern to the runway. At 30 minutes out of arrival the FRO would clear with the CW operator and the pilots would take over communications with the tower. Upon landing the FRO would log in arrival time using UTC.
A typical DC-3 flight out of Brownsville, TX would be an hour and a half to Tampico, Mex. half an hour on the ground, an hour to Mexico City, an hour on the ground with refueling, three hours to Tapachula, Mex. an hour on the ground with refueling and, finally, an hour to Guatamala City, Guatamala where we overnighted. We spent over 7 hours flying time avarage. During WWII, we could fly half an hour before sunrise to half an hour after sunset.