Jay Honeck wrote:
Eighty-one years ago today, on April 6, 1926, the first official
commercial mail transport flight occurred

I don't believe this date is accurate, since the first
transcontinental air mail flight went through Iowa City fully 5 years
before this, in February 1921.

Did you read his article...he's talking about the COMMERCIAL
(non-government) carriage of the air. He even mentions the
federal mail flights.

The VERY FIRST air mail flight departed from Washington DC
in 1918 (they were using Army planes now that the great war
was over). It departed from a field in DC which is now use
as a polo field. The plane was heading off towards Baltimore
with a bag of mail but was forced down by weather and the
mail went on by surface.