Early on in the series, Helen (Crystal Bernard) makes a reference to her sister "Loraine". Years later Amy Yasbeck joins the series playing Helen's only sister "Casey".
In episode 4.2: "The Fortune Cookie", Joe decides to dissolve Sandpiper and Lowell fears he's out of a job, but in episode 3.14: "Stew in a Stew", Joe clearly states that Lowell works for the airport, not Sandpiper, meaning he still has the six planes at Aeromass to maintain.
Sandpiper only has one airplane, and Joe always reads its call number as "Nevada-One-Two-One-Papa-Papa" or N121PP. However, there are a few episodes where the Sandpiper plane's tail shows N121PB and several more (mostly exterior shots) where it shows N160PB.
The call sign used for the plane "Nevada-One-Two-One-Papa-Papa" is incorrect with the ICAO phonetic alphabet. It should be "November-One-Two-One-Papa-Papa"
Airline pilots will actually use the flight number when calling ATC, such as Southwest 1567. Don't know why the producers didn't have the pilots in this show use a flight number instead of the tail number. Private Pilots sometimes do say November, as in November 121 papa papa but usually will say the aircraft model or manufacturer, in this case Cessna or Chancellor 121 papa papa. Once com has been established with ATC this can be shortened to the last 3 characters, in this case 1 papa papa.
Joe uses call letters to identify the aircraft incorrectly. He says "November-One-Two-One-Papa-Papa" to announce N121PP. However, pilots NEVER include the first letter. The call should be "One-Two-One-One-Two-One-Papa-Papa" and that is further abbreviated to just "Papa-Papa" one communication is established.
No one in this Nantucket-based show has a New England accent.
A character has a strong Arabic accent but is supposed to be Italian. Upon close examination, that actor turns out to be of Middle Eastern descent: Tony Shalhoub is the man playing Antonio Scarpacci. His first language was indeed Arabic (Lebanese).