"We are here because destiny has drawn us here," his youngest daughter, Reverend Bernice King said as she addressed a huge crowd at the spot where he was shot to death at the Lorraine Motel in Memphis, a day after rallying striking sanitation workers.

Thousands honored King's achievements but noted the need for more progress on equal rights.

King's son Martin Luther King III proposed to hold a march on Washington this year similar to the historic gathering his father headed in 1963.

That was when he delivered his landmark "I Have A Dream" speech that galvanized the civil rights movement with a message of equality and non-violence.

Five years later, at just 39, he was shot dead while he was standing on the balcony of the Lorraine Motel on April 4, 1968.

First hydrogen-battery powered plane flown in Spain: BoeingU.S. aircraft giant Boeing claimed on April 3 a world first in putting into the air a plane powered by a hydrogen-cell battery, a breakthrough that could herald a greener future for the industry.

"For the first time in the history of aviation, Boeing has flown a manned airplane that was powered by a hydrogen battery," Boeing chief technology officer John Tracy said.

Boeing staged three successful test flights of the 6.5-meter long plane in February and March at an airfield at Ocana, just south of Madrid.

The company said that although hydrogen fuel cells could be used to power small planes, it did not believe they could become the primary power source for large passenger aircraft.

Hydrogen power uses "fuel cells" that tap the energy produced from the chemical transformation of hydrogen and oxygen into water.

It holds the promise of a cleaner and renewable energy resource as it produces only harmless water vapor as waste.