Plovdiv reached an agreement that the Principality of Bulgaria and Eastern Rumelia had a common government, Parliament, administration, and army. Today 6 September is celebrated as the Unification Day and the Day of Plovdiv. After the unification, Plovdiv remained the second most populous city in Bulgaria after the capital Sofia. The first railway in the city was built in 1874 connecting it with the Ottoman capital, and in 1888, it was linked with Sofia. In 1892 Plovdiv became host of the First Bulgarian Fair with international participation which was succeeded by the International Fair Plovdiv. After the liberation, the first brewery
Plovdiv Airport and a tie-up between Hainan and Plovdiv Airport Invest. On 28 March 2018, Bulgarian Government awarded the consortium of HNA Group and Plovdiv Airport Invest a 35-year-long concession on Plovdiv airport in return for investments reaching €79 million, including a new cargo and passenger terminal. On 19 of July the consortium of HNA Group and Plovdiv Airport Invest have declared that it won't sign the concession contract which opens the road for the classified on the second place to take the concession. On the west side of the airport is located 24th Helicopter Air Base of the Bulgarian Air Force,