(Reuters) -Wall Street's main indexes eyed a higher open on Wednesday bolstered by megacap growth stocks, while investors parsed corporate earnings and awaited commentary from Federal Reserve policymakers for clues on the state of the economy.

Megacap growth names such as Microsoft, Amazon.com and Tesla advanced between 0.5% and 0.7% before the bell.

The benchmark S&P 500 and the Nasdaq closed lower in the previous session, bogged down by climbing Treasury yields.

Government bond yields were largely unchanged, with the 10-year note last at 4.6552%.

Fed Board Governor Michelle Bowman and Cleveland Fed President Loretta Mester are scheduled to speak later in the day.

Top U.S. central bank officials including Fed Chair Jerome Powell refrained from providing any guidance on when interest rates may be cut. On Tuesday, they said monetary policy needed to be restrictive for longer, dashing investors' hopes for meaningful reductions in borrowing costs this year.

Money market participants see an around 43% chance the central bank could begin its easing cycle in July, according to the CME FedWatch tool.

First-quarter earnings season was in full swing, with United Airlines gaining 6.2% after it forecast stronger-than-expected numbers in the current quarter.

Other airline stocks such as American Airlines, Delta Air Lines and Southwest Airlines added between 1.1% and 2.4%

JB Hunt Transport Services shed 8% after the trucking firm missed Wall Street estimates for first-quarter results.

U.S. Bancorp dropped 3.5% after the lender cut its forecast for full-year interest income and reported a 22% fall in first-quarter profit.

Travelers fell 5% after the insurance giant missed Wall Street expectations for first-quarter core profit.

"Valuations are pretty high now, so there's not a lot of leeway for bad news," said David Russell, global head of market strategy at TradeStation.

"We've priced in a lot of good news and strong economic growth might not necessarily immediately be a positive - if it also means that we're going to be looking at higher interest rates and what that means for valuations."

Later in the day, investors will watch for the release of the Fed's "Beige Book" report, to assess the health of the world's largest economy.

At 8:34 a.m. ET, Dow e-minis were up 52 points, or 0.14%, S&P 500 e-minis were up 14.25 points, or 0.28%, and Nasdaq 100 e-minis were up 33.75 points, or 0.19%.

Mobileye advanced 3.2% after Reuters reported the Israeli automotive tech company was set to ship at least 46 million new assisted-driving chips.

Eli Lilly gained 2.2% after its weight-loss drug helped cut the frequency of irregular breathing in patients with obstructive sleep apnea by as much as 63% on average, across two late-stage trials.

ResMed and Inspire Medical, who make medical devices used to treat sleep apnea, fell 3.7% and 2.4%, respectively.

Apparel retailer Urban Outfitters eased 4.4% after Jefferies downgraded its rating to "underperform" from "hold".