The United Provinces of Agra and Oudh was a province of India under the British Raj, which existed from 1902 to 1921; the official name was shortened by the Government of India Act 1935 to United Provinces (UP), by which the province had been commonly known, and by which name it was also a province of independent India until 1950.It corresponded approximately to the present-day Indian states of Uttar Pradesh (UP) and Uttarakhand. Allahabad served as the administrative headquarters and the capital of the province. Two years after the annexation of Oudh State in 1856, i.e. after 1858 and until 1902, the region had existed as North-Western Provinces and Oudh, Oudh being a Chief Commissionership.

Airmail (or air mail) is a mail transport service branded and sold on the basis of at least one leg of its journey being by air. Airmail items typically arrive more quickly than surface mail, and usually cost more to send. Airmail may be the only option for sending mail to some destinations, such as overseas, if the mail cannot wait the time it would take to arrive by ship, sometimes weeks. The Universal Postal Union adopted comprehensive rules for airmail at its 1929 Postal Union Congress in London. Since the official language of the Universal Postal Union is French, airmail items worldwide are often marked Par avion, literally: "by airplane".

For about the first half century of its existence, transportation of mail via aircraft was usually categorized and sold as a separate service (airmail) from surface mail. Today it is often the case that mail service is categorized and sold according to transit time alone, with mode of transport (land, sea, air) being decided on the back end in dynamic intermodal combinations. Thus even "regular" mail may make part of its journey on an aircraft. Such "air-speeded" mail is different from nominal airmail in its branding, price, and priority of service.