First Air-Mail Service in the World began in British India in 1911

1911 India's first Air-Mail Service. indiatoday.in

The world's first official airmail flight took place on February 18, 1911, from Allahabad to Naini in India. This landmark event was held during the 1911 Maha Kumbh Mela, marking the first official airmail delivery and the first-ever flight in India. French pilot Henri Pequet piloted a Humber-Sommer biplane, carrying around 6,500 letters over a distance of five miles. The journey, which took just 13 minutes, began at the Holy Trinity Church in Allahabad. The letters bore a special stamp reading "First Aerial Post, U.P. Exhibition, Allahabad. 1911."This successful experiment in India inspired the establishment of the world's first scheduled airmail post service in the United Kingdom later that year, between Hendon and Windsor on September 9, 1911, as part of King George V's coronation celebrations. 

First airmail service.  Allahabad and Nainiwww.delcampe.net

Above image: Humber-Sommer biplane, First air-mail service in the world. 1911, British India carried 6500 letters..........

Airmail history began with balloon flights in the late 18th century. The first such recorded mail transport was on January 7, 1785, when a hot air balloon carried mail from Dover to Calais, piloted by Jean-Pierre Blanchard and John Jeffries. The first U.S. airmail delivery took place on August 17, 1859, when John Wise piloted a balloon carrying mail from Lafayette to Crawfordsville, Indiana, though weather forced him to land short of his intended destination.  

Allahabad cover world's first aerial post in 1911 (Wikipedia)