With a pun on Pilate 1, the jocular phrase since Pontius was a pilot means for a very long time.
1 Pontius Pilate (died circa 36 AD), Roman procurator of Judaea from circa 26 to circa 36, is remembered for presiding at the trial of Jesus Christ and authorising his crucifixion—cf. origin of ‘from pillar to post’.
The phrase since Pontius was a pilot seems to have originated in the Royal Air Force—i.e., the British air force—during the Second World War. This is what Henry Kisor wrote in the review of A Dictionary of Soldier Talk (New York: Scribner, 1984), by John Robert Elting, Dan Cragg and Ernest L. Deal—review published in The Morning Call (Allentown, Pennsylvania) of Tuesday 13th March 1984:
“Since Christ was a corporal” is a jocular term indicating it is a long time since something has happened, or perhaps it never happened. During World War II the British Royal Air Force version was “Since Pontius was a pilot.”
The earliest occurrence of the phrase that I have found supports this origin. It is from the account of life in Malta that one Flight Sergeant Coulter wrote after serving for nearly four years in that Mediterranean island—account published in the Shipley Times and Express (Shipley, Yorkshire, England) of Wednesday 22nd March 1944:
For the people of Malta I have a very sincere admiration. Pleasant, hospitable, gentle, the hardships they have suffered cry to high Heaven. Bombed and bombed again, twenty-four hours a day, and every day for weeks and months without ceasing, their homes destroyed and their trivial treasures scattered; their children, too. I have seen demented mothers searching for their babies buried beneath an avalanche of senseless stone. These people have paid dearly for the doubtful privilege of having their island acclaimed the most bombed spot on earth.
How they went wild with joy when the first Spitfire Squadron arrived, and what a job those pilots made of it. They sailed into Kesselring’s boys and cut them to ribbons. It took them just over a week to gain the upper hand, and during that week the sea between Malta and Sicily was dotted with German and Italian dinghy crews, paddling like blazes. As one pilot reported, it looked like the Thames on boat-race day. Another wit swore that there hadn’t been a “do” like it since Pontius was a pilot.
All the other early uses of the phrase that I have found occur in aviation contexts.
The following is from the account of a debate on the Civil Aviation Agreement Bill that took place at the House of Representatives, in Canberra, Australian Capital Territory—account published in The Age (Melbourne, Victoria) of Friday 31st October 1952:
Mr. Beazley (Lab., W.A.) said A.N.A. 2 had better make certain it kept solvent in future because everyone could realise the instruction a Labor Government would give to the Commonwealth Bank about foreclosure if A.N.A. was at all behind in its repayments.
Mr. Falkinder (Lib., Tas.) said the remarks of Labor members about the quality of A.N.A. aircraft were made as though these members had been flying since Pontius was a pilot.
In fact, these people know as little about aircraft as Pontius did.
2 A.N.A. is the abbreviation of Australian National Airways.
The British author and newspaper columnist Keith Waterhouse (1929-2009) 3 used the phrase in his column Keith Waterhouse on Monday, published in the Daily Mirror (London, England) of Monday 1st February 1971—in order to show that “the third London airport would prove, after all, to be completely unnecessary”, Keith Waterhouse mentioned the opinion given by
the distinguished aircraft designer Sir Barnes Wallis, who as they say in the RAF has been in the aeroplane game since Pontius was a pilot.
3 Keith Waterhouse coined red masthead, precursor of the British journalistic term red top.
The phrase occurs in Airlines face strike in March, by Thomas M. Burnett, of United Press International, published in the Reporter (Martinsville, Indiana) of Saturday 7th February 1981:
A top official of the Air Line Pilots Association says he sees little chance of avoiding a threatened nationwide air strike next month unless the government offers some quick proof of concern for air safety.
ALPA Secretary Thomas Ashwood quipped to reporters during a news conference Friday that his group’s members have been fighting with the Federal Aviation Administration on airline safety “since Pontius was a pilot.”
The phrase came to be also used outside aviation contexts—for example by Jeffrey Smith, Daily Record correspondent, in an article about the “four-man comedy team, Open Season”, published in the York Daily Record (York, Pennsylvania) of Friday 20th October 1989:
Two characters from the Open Season menagerie are Slash Tyre (pronounced tie-err) and Newt (pronounced new-ute), the punk poets, who have been around since before Pontius was a pilot.