Question: Who was also an airline pilot, Billy Gibbons or Bruce Dickinson?

full_context: Document 1: Billy Cox: William "Billy" Cox (born October 18, 1941) is an American bassist, best known for performing with Jimi Hendrix. Cox is the only surviving member of Jimi Hendrix's three main bands, including the original Experience lineup (which did not include Cox); he was in the Band of Gypsys and afterwards the Cry Of Love trio (a.k.a. the Jimi Hendrix New Experience). Cox was also in the short-lived Hendrix band Gypsy Sun and Rainbows (there are other surviving members from this group) which played Woodstock, prior to the Band of Gypsys formation. Cox continues to perform dates with the Band of Gypsys Experience and the Experience Hendrix Tour.
Document 2: Rob Halford: Robert John Arthur Halford (born 25 August 1951) is an English singer and songwriter, who is best known as the lead vocalist for the Grammy Award-winning heavy metal band Judas Priest and famed for his powerful wide-ranging voice. AllMusic says of Halford: "There have been few vocalists in the history of heavy metal whose singing style has been as influential and instantly recognizable", possessing a voice which is "able to effortlessly alternate between a throaty growl and an ear-splitting falsetto". Halford was voted number 33 in the greatest voices in rock by Planet Rock listeners in 2009. In addition to his work with Judas Priest, he has been involved with several side projects, including Fight, 2wo and Halford. In 1998, he came out as gay in an interview with MTV News.
Document 3: ZZ Top: ZZ Top is a rock band formed in 1969 in Houston, Texas. The band has, since 1970, consisted of bassist and lead vocalist Dusty Hill, guitarist and lead vocalist Billy Gibbons (the band's leader, main lyricist and musical arranger), and drummer Frank Beard. "As genuine roots musicians, they have few peers," according to former musician, critic and collector Michael "Cub" Koda. "Gibbons is one of America's finest blues guitarists working in the arena rock idiom [...] while Hill and Beard provide the ultimate rhythm section support."
Document 4: Bruce Dickinson discography: Bruce Dickinson, a British heavy metal singer, has released six studio albums, two live albums, one compilations, ten singles, three video albums, fourteen music videos, and one box set. In 1979, after playing in local groups, Dickinson joined hard rock band Samson. He departed after two years to become Iron Maiden's lead vocalist. His debut with this band is considered a "masterpiece", which was followed with a series of top-ten releases. In 1989, while Iron Maiden were taking a year off, Dickinson and former Gillan guitarist, Janick Gers, composed a song for . His solo debut, "Tattooed Millionaire" (1990), was an effort that favoured a hard rock/pop metal approach, different from what fans assumed would be an aggressive, Iron Maiden-like album. Four songs—the title track, "Dive! Dive! Dive!", "Born in '58", and a cover version of David Bowie's "All the Young Dudes"—were released as singles. Dickinson returned to Iron Maiden, accompanied by Gers as the new guitarist, and the project went on hiatus. "Dive! Dive! Live!" was a live video recorded from a concert in Los Angeles, California, in August 1990, and released in July 1991.
Document 5: Paul Day (musician): Paul Mario Day (born 19 April 1956, Whitechapel, East London) is a British singer who is well-known as the original lead vocalist of Iron Maiden from 1975 to 1976.
Document 6: Born in '58: "Born in '58" is the last single from Bruce Dickinson's debut solo album, "Tattooed Millionaire", released on March 25 1991. The song is about Bruce Dickinson's early life, growing up with his Grandparents in Worksop (Dickinson was born in 1958).
Document 7: Billy Gibbons: William Frederick Gibbons (born December 16, 1949) is an American musician, singer, songwriter, producer, and actor, best known as the guitarist and lead vocalist of the American rock band ZZ Top. He began his career in the Moving Sidewalks, who recorded "Flash" (1968) and opened four dates for the Jimi Hendrix Experience. Gibbons formed ZZ Top in late 1969 and released "ZZ Top's First Album" in 1971. The albums that followed, "Rio Grande Mud" (1972) and "Tres Hombres" (1973), along with extensive touring, solidified the group's reputation as a hard-rocking power trio.
Document 8: Paul Di'Anno: Paul Andrews (born 17 May 1958), better known by his stage name Paul Di'Anno, is a British singer best known as the first vocalist to record with heavy metal band Iron Maiden, from 1978 to 1981.
Document 9: Jimmy Page: James Patrick Page, {'1': ", '2': ", '3': ", '4': "} (born 9 January 1944) is an English musician, songwriter, and record producer who achieved international success as the guitarist and founder of the rock band Led Zeppelin.
Document 10: Rob Dickinson: Rob Dickinson (born 23 July 1965) is a British musician and singer-songwriter previously of the band Catherine Wheel. Dickinson was raised in Norfolk, England, and is the paternal cousin of Iron Maiden frontman Bruce Dickinson. He is now a solo artist and the founder and creative director of Singer Vehicle Design, which performs restoration and modification of client vehicles.
Document 11: Ian Gillan: Ian Gillan (born 19 August 1945) is an English singer and songwriter. He originally found commercial success as the lead singer and lyricist for Deep Purple.
Document 12: Bobby Gillespie: Robert Bernard Andrew "Bobby" Gillespie (born 22 June 1962) is a Scottish musician and singer-songwriter. He is the lead singer and founding member of the alternative rock band, Primal Scream. He was also the drummer for The Jesus and Mary Chain in the mid-1980s.
Document 13: Bruce Dickinson: Paul Bruce Dickinson (born 7 August 1958), known professionally as Bruce Dickinson, is an English singer, songwriter, musician, airline pilot, entrepreneur, author and broadcaster. He is the lead singer of the heavy metal band Iron Maiden and is renowned for his wide-ranging operatic vocal style and energetic stage presence.
Document 14: The Jimi Hendrix Experience: The Jimi Hendrix Experience was an American-English rock band that formed in Westminster, London, in September 1966. Singer, songwriter, and guitarist Jimi Hendrix, bassist and backing vocalist Noel Redding, and drummer Mitch Mitchell comprised the group, which was active until June 1969. During this time, they released three studio albums and became one of the most popular acts in rock. In April 1970, Hendrix, Mitchell, and bassist Billy Cox performed and recorded until Hendrix's death on September 18, 1970. This later trio was sometimes billed as the "Jimi Hendrix Experience", but the title was never formalized.
Document 15: El Loco: El Loco is the seventh studio album by the American rock band ZZ Top, released in 1981. The title means "The Crazy One" in Spanish. The band's guitarist/singer Billy Gibbons has said that the recording of this album was the first time the three members of the band were isolated from one another in the studio, rather than recording simultaneously in the same room. It also foreshadowed ZZ Top's synthesizer-driven direction later in the decade, with early experimentations in synthesizer backing on certain tracks.
ground_truth: Bruce Dickinson