Trisuci Vesak Day commemorates three important events, they are the birth of Prince Siddhartha, Prince Siddhartha attaining Great Enlightenment and becoming a Buddha, and Buddha Gautama parinibbana (died). In the celebration, there is a tradition of releasing Vesak lanterns which is usually held at Borobudur Temple.

The releasing of the lanterns was the culmination of Vesak ceremonies at Borobudur Temple, Magelang, Central Java. Tourists can follow along and capture the moment they release thousands of lanterns into the air. This moment becomes a very interesting experience for tourists, don’t forget to always capture this moment by taking the photo of the lanterns or taking photos in the middle of releasing the lanterns.
The flying lanterns are known as Puja lanterns. This Puja lantern is flown and released this year on the closing night of Trisuci Vesak. This tradition has often been performed. The release of lanterns aims to eliminate the bad things in human beings.
For this, each lantern is written with prayer and the hope of living a better life. The release of these lanterns is done with the hope that Buddhists always wish to get health, blessings, sincere thoughts.
Meanwhile, the fire in the lanterns symbolizes the spirit of selfishness seeking guidance in living a pure life.
-sh
Quoted From Many Source