# UC46 FDC - 1973 15c Air Post Envelope Hot Air Ballooning
First US Aerogram
In the early days of the mail, letter sheets were the common way to send letters. Messages were written on paper that was folded and sealed. Some postal authorities would charge by the amount of paper used, so using an envelope would make mailing a letter more expensive. As these laws changed and envelopes became the common practice, letter sheets fell out of favor but were still used on occasion in the 1900s.
See more US aerograms below:
First US Aerogram
In the early days of the mail, letter sheets were the common way to send letters. Messages were written on paper that was folded and sealed. Some postal authorities would charge by the amount of paper used, so using an envelope would make mailing a letter more expensive. As these laws changed and envelopes became the common practice, letter sheets fell out of favor but were still used on occasion in the 1900s.
See more US aerograms below: