Prime Minister Indira Gandhi's only surviving son, Rajiv, formerly entered India's political arena today to contest the parliamentary seat left vacant by the death of his younger brother, Sanjay, in an airplane crash nearly a year ago.

If successful, the 36-year-old professional pilot is almost certain to eventually assume the position of his late brother as one of India's most powerful men despite his near-total lack of political experience.

The announcement of Gandhi's plans ended months of speculation that he would bow to pressures from within his mother's Congress-I Party to fill the void left by Sanjay's death.

The parliamentary byelection, in the Amethi constituency of Uttar Pradesh state about 300 miles east of the capital, is scheduled for June 14.

Gandhi resigned last week from the job that he had held for nearly a decade as a pilot with India's state-owned domestic carrier, Indian Airlines. He joined the Congress-I Party early today before departing by air for Amethi to file his election papers later in the day.

Answering questions at his first news conference, Gandhi said that his decision to end his flying career and enter politics was made entirely on his own, without consulting his mother, who is on an official visit to the United Arab Emirates.

Although he initially resisted pressures to enter politics in the months following Sanjay's death, Rajiv slowly became informally involved in the political life surrounding his mother during the past year. Soft-spoken and with a reputation for honesty, Gandhi always maintained that he wanted to remain as an airline pilot.