The Congress on Monday demanded a probe against Prime Minister Narendra Modi for flying on a sea-plane during election campaign in Gujarat without Special Protection Group (SPG) security.Party General Secretary in-charge of Gujarat Ashok Gehlot asked how was the Prime Minister allowed to fly on a sea-plane without the SPG and demanded action against those who allowed it."What was the objective behind it? It had no significance during Gujarat elections. The seaplane came all the way from the US to Pakistan, and then to Mumbai to the river front in Gujarat," he said."How can the Prime Minister fly on a sea-plane without taking the SPG along. To win elections, he can go to extent. Both the pilots were foreigners," he added.