By John McCrank and Anna Irrera

NEW YORK (Reuters) - Robinhood Markets Inc, the fintech startup credited with helping popularize trading with millennials, said on Thursday it resolved an issue that had caused a "major outage" on its platform earlier in the day.

"Our systems have been fully restored and our app and web platforms are now functional. We apologize for the trouble and appreciate your patience as we worked to resolve this," the company said on Twitter.

Robinhood, based in Menlo Park, California, has experienced several outages since early March, particularly on days of high trading volumes as the market reacted to news on the economic impact of the coronavirus pandemic.

Similar to previous outages, customers took to social media to criticize Robinhood, threatening to switch brokerages.

"Unacceptable for this to keep happening," one user said on Twitter. "Give me one reason why I should continue to trade using your platform?" asked another.

Robinhood has been at the center of a recent upsurge in day trading by retail investors, who have been homebound due to coronavirus lockdowns.

Founded by co-chief executives Baiju Bhatt and Vladimir Tenev in 2013, Robinhood is one of the most popular and well-funded financial technology startups. Last month, it raised $280 million from investors at a valuation of $8.3 billion dollars.

The company now has over 10 million user accounts. Customers at the brokerage, which has been credited for helping usher in commission-free trading throughout the retail brokerage industry, have a median age of 31, the company said recently.

(Reporting by John McCrank and Anna Irrera, Editing by Aurora Ellis and Nick Zieminski)