The Airship Revolution (1771) is an event in Final Fantasy IX that took place 29 years before the events of the game. Resolving a series of conflicts that had lasted for centuries, the Airship Revolution brought about a peace treaty between the Mist Continent nations.
At an undefined point, the nations of Alexandria and Burmecia—two nations with a long history of hostilities—went to war. Leading Alexandria was Queen Brahne's father, the King of Alexandria. It is unclear whether the present-day King of Burmecia, who was 21 years old in 1771, ascended the throne before, during, or after the war, though his age may suggest the latter.
In a dummied conversation between Adelbert Steiner and Morrid, the former claims that Burmecia started the war. This is not disputed by the latter, who counters that Alexandria started other wars in the past. It is thus likely that Burmecia did indeed initiate this war.
It is unclear when exactly the war started. According to a timeline from Final Fantasy IX Ultimania, Baku became an orphan of war in year 1762, at the age of seven. However, this could refer to some different war.
According to a dummied piece of dialogue in the game, the King of Alexandria died in the war in year 1770. No elaboration is offered, other than that Burmecia was somehow responsible for his death. Steiner, who was four years old when the king died, lost his parents in the last year of the war and got caught up in it himself. He was saved by the Knights of Pluto, which inspired him to become a knight himself.
Watching the war on the sidelines was the Regency of Lindblum. Regent Cid Fabool VIII, who had become Lindblum's eleventh regent in year 1756, built an armada of Mist-powered airships in 1762, widening the technological gap between Lindblum and the other nations of the Mist Continent. In 1771, Cid used this armada to intervene in the Alexandrian-Burmecian War. It is unclear whether Lindblum fought any of the belligerent nations, or if the intervention was merely a show of force meant to pressure the warring parties to end hostilities. The result was a tripartite peace treaty between the three nations, ending a long chain of wars between the countries of the Mist Continent. This alone may suggest that Lindblum did not pick sides in the war, but rather acted as a third party.
The Airship Revolution brought about a genuine peace between Lindblum, Alexandria and Burmecia, and made Lindblum the strongest power of the continent. Lindblum and Alexandria began diplomatic relations in 1772. The Berkmea Cable Cars were later constructed in the Aerbs Mountains to commemorate the 20th anniversary of the peace between the two nations.
While Lindblum and Burmecia developed close ties as well as a military alliance, some Burmecians got worried as its military power was getting increasingly overshadowed by that of the other nations of the continent. Citing the growing power of Alexandria in particular, in 1795, Sir Fratley left Burmecia to travel and get stronger to become a better knight.
The only loser of the war was Garland. Unknown to anyone in the world of Gaia, the Mist that covered the Mist Continent was actually the manifestation of anguished Gaian souls, created by Garland through the Soulcage at the Iifa Tree for two purposes; the Gaian souls were prevented from returning to the planet, paving the way for Terran souls to take their place; and the Mist itself hardened the people who were exposed to it, making them more war-prone.
The Airship Revolution thus forced Garland to come up with a different plan. He decided to create a Genome with a mind of its own, and send it to the Mist Continent to incite more wars. This "Angel of Death", Kuja, was constructed five years after the Airship Revolution. While initially deemed a failure by Garland, Kuja did eventually succeed in gaining influence over Alexandria's Queen Brahne XVI. He convinced her to embark on a war to conquer the other nations of the Mist Continent, using an army of black mages created from Mist. Alexandria invaded Burmecia in year 1800, ending the 29 years of peace.