Four US first air mail route flight covers from the 1930s. See pictures for condition.

Most items under $20 ship in a first-class envelope with collectible stamps and with card stock  and, for loose stamps, glassine for protection; more expensive or heavier items may go Ground Advantage or Priority Mail. 

Check out my store for stamps, postal stationery, and covers (first day, space, flight, and more) from the US and worldwide! Most inventory comes from my historian dad's 65-year collection. He specialized in the US, Nepal, and mountain climbing but collected from all continents.