Europe's Ariane 5 rocket has made its 50th flight from the Kourou spaceport in French Guiana.

The rocket lifted away from the launch pad at 2201 GMT, carrying two telecommunications satellites with a combined mass of almost eight tonnes.

After failing on its very first mission in 1996, the Ariane 5 has developed into a highly reliable vehicle with a dominant role in the launcher market.

About half the world's large commercial comms satellites now launch on Ariane.

Friday's dual payload included the SES Astra 3B spacecraft, which will deliver TV and broadband services to Europe and the Middle East, and the ComsatBW-2 platform which will provide secure data links for the German armed forces.

The 5.4-tonne Astra 3B was the first to be deployed by Ariane some 27 minutes into the flight; the 2.4-tonne ComsatBW-2 was released six minutes later.

Ariane's departure ended two frustrating months for the rocket's operator, Arianespace.

The mission had been postponed three times since late March. The previous launch attempt in early April even got to within a minute of blast-off before the countdown sequence was halted.

Inquiries set up to investigate the delays and quality control issues in the rocket's preparation resulted in a regulator that maintains pressure in the vehicle's super-cold (cryogenic) hydrogen and oxygen propellant tanks being exchanged.

The generic Ariane 5 launcher went into full commercial service in 1999, and was followed a few years later by the beefed-up version, the ECA, which is capable of lofting nearly 10 tonnes of payload into a geostationary transfer orbit (GTO) some 36,000km above the Earth.

The rocket has two solid boosters to lift it off the ground, a cryogenic main stage to do most of the work of getting into orbit, and an upper-stage to place the satellites in the target orbit, or GTO.

Friday's mission marked the 36th consecutive successful launch for an Ariane 5.

Highlights in the vehicle's 14-year-history include the launch of Europe's flagship Herschel and Planck space telescopes last year; the bloc's 2bn-euro Envisat Earth-observation spacecraft in 2002; and its "Jules Verne" robotic supply ship that went to the International Space Station (ISS) in 2008 weighing more than 20 tonnes.

European ministers have approved a programme to upgrade the rocket. This "mid-life evolution" should enter service later this decade and give the vehicle a GTO capability of 13 tonnes.

Despite the late start to its 2010 launch campaign, Arianespace promises to fly six further Arianes this year, including a second ISS freighter called "Johannes Kepler".

Jonathan.Amos-INTERNET@bbc.co.uk