Also known as Airships, Zeppelins and Blimps.
These are those cigar shaped airliners of yesteryears (circa 1900's). These helium or hydrogen filled lighter-than-air-craft, powered by two or more engines were extensively used as passenger transport plying the trans atlantic route. Some were used as bombers during World War I.
One of the most famous dirigible that comes to mind is the ultra luxurious 800 foot long German made HINDENBURG ZEPPELIN. It was the largest dirigible to ever fly. It was the Jumbo Jet of its day! It had 97 people (61 crew) on board when it left Germany and crashed into huge a ball of flames when attempting to land in New Jersey, USA in 1937. Only 62 people survived this fiery crash. This marked the end of passenger air service dirigibles or airships of that era.
Today, new technological breakthroughs in airship design using solar power for energy may soon make a comeback.