A lesser-remembered chapter of the old Belgian flag-carrier Sabena is the airline's experiment with helicopter services. The handsome poster above is surely from the late 1950s, showing the DC-7 which arrived in 1957 to serve the airline's long-haul routes but was supplanted only three years later in 1960 by the Boeing B707.
Details of Sabena's unique rotor-craft network is reprinted from the Sabena website:
SABENA flew international services with Sikorsky S.55 SABENA began international passenger services with the Sikorsky S.55
Sikorsky S.58 SABENA improved the helicopter services with eight Sikorsky S.58s