Stocks making the biggest moves midday: TD Ameritrade, Delta Air Lines, Stitch Fix & more
Traders work on the floor of the New York Stock Exchange.

Check out the companies making headlines in midday trading:

TD Ameritrade — Shares of brokerage firm TD Ameritrade sank 2.5% after announcing the company will eliminate all commission fees for online U.S. stock, exchange-traded fund and option trades. The stock sank on fears TD relies heavily on commission revenue. Rival retail broker Charles Schwab fell 2.5% and E-Trade fell 2.4%.

Delta Air Lines — Shares of the airline company plunged more than 6% after the company lowered the top end of its earnings guidance for the third quarter. The company now expects EPS between $2.20 and $2.30, versus prior estimates of $2.10 - $2.40. Operating costs are also projected to rise.

Stitch Fix — Shares of Stitch Fix tanked 10% after giving lower-than-expected current-quarter forecast. The online-styling service said it's planning for "softer" results in the first quarter of fiscal 2020. Despite the negative outlook, Stitch Fix's fourth-quarter earnings per share beat analysts' estimates and revenue came in line with estimates.

Lennar — Shares of homebuilder Lennar rose 2.5% after beating on the top and bottom lines of its third quarter earnings results. The company reported earnings per share of $1.59 on revenue of $5.857 billion. Wall Street estimated $1.32 per share on revenue of $5.483 billion, according to Refinitiv. Volume of new orders also rose 9% from a year earlier.

Ford — Shares of Ford slid 4.5% after the automaker said its U.S. vehicle sales declined 4.9% during the third quarter from a year ago. Demand for Ford's highly-profitable best-selling F-Series pickup line started to wane, tumbling 6% in sales in the quarter.

Paychex — Shares of Paychex rose about 2% after the payroll services company reported better-than-expected fiscal first-quarter earnings. Paychex reported an earnings of 71 cents per share, beating the estimates of 69 cents. Its sales also topped expectations,

Activision Blizzard — Shares of Activision Blizzard dropped nearly 3% after Bernstein downgraded the video game company to market perform from outperform. Bernstein said it cannot reconcile the current stock price with company fundamentals after a 25% rally since late May.

— CNBC's Maggie Fitzgerald and Pippa Stevens contributed to this report.