Tanker operator Euronav is to buy U.S. rival Gener8 Maritime to create one of the world's top oil shipping fleets, the companies said on Thursday, in an all-stock deal worth an estimated $490 million. Tanker companies have faced tough conditions in recent months, partly due to a glut of ships available for hire, and as a result have been looking for ways to build scale and cut costs. The Euronav deal is the first major M&A transaction since Oslo-listed tanker player Frontline said in June it had abandoned its pursuit of New York-listed rival DHT Holdings . Euronav, headquartered in Belgium, said the deal would create a tanker group with "tangible economies of scale" and an estimated market capitalisation of about $1.8 billion.