Check out the companies making headlines in midday trading. Boeing — Shares of the aerospace and defense giant lost 6.51% after a door panel on a Boeing 737 Max 9 blew out midair during an Alaska Airlines flight , leading the Federal Aviation Administration to ground dozens of the planes . Shares of Spirit AeroSystems , which made and installed the door, fell 5.50%. Alaska Air Group — The airline slid 0.11% following the Boeing incident and announcements that it had canceled dozens of flights after grounding its 737 Max 9 fleet. Axonics — Shares soared 20% after Boston Scientific agreed to acquire the biotechnology firm for $71 per share , or an equity value of around $3.7 billion. American Airlines — The airline jumped nearly 7.61% after Morgan Stanley upgraded the shares to overweight from equal weight. The Wall Street firm said it’s excited about the upcoming investor day, which could be a catalyst for upside in the stock. Enphase Energy , First Solar — Enphase Energy gained 1.66% after getting an upgrade from Wells Fargo to overweight from equal weight. The bank said it expected a rebound in residential solar as interest rates fall. Wells Fargo, however, downgraded First Solar due to its strong 2023 performance and the relatively defensive nature of its cash flows. First Solar was fractionally lower. Shell — Shares of the oil and gas giant slipped 1.69% after the company said it expects a noncash post-tax write-down of between $2.5 billion and $4.5 billion in the fourth quarter of 2023. Dell — The personal computer maker added 4.64% on the heels of two bullish Wall Street calls. UBS named Dell a top pick among technology hardware names in 2024 on Sunday, noting its recovery and buybacks. JPMorgan upgraded Dell to overweight from neutral on Monday, citing leverage from an investment cycle driven by artificial intelligence. Equifax — The credit reporting agency gained nearly 3.94% after Bank of America double upgraded it to a buy rating from underperform. The bank cited a bullish mortgage outlook on the back of expected rate cuts as a reason for the change. Toll Brothers — Shares of the homebuilder rose more than 2.37% Monday after Wolfe Research upgraded Toll Brothers to outperform from peer perform. The investment firm said luxury homes may rebound now that mortgage rates have declined from their 2023 peak. Host Hotels & Resorts — The hotel real estate investment trust gained 2.82% following a double upgrade from Bank of America to buy from underperform. Analyst Shaun Kelly raised the bank’s price target to $23 from $18, highlighting the stock’s compelling valuation and steadily improving capital allocation. Chevron — Shares of the second-largest energy stock in the U.S. dropped 0.60% Monday despite an upgrade to buy from hold at Jefferies. “CVX lagged the majority of its peers in ’23 due to increased uncertainty around production visibility (Permian, Tengiz), depth of inventory, and capital overruns,” wrote analyst Lloyd Byrne, who believes Chevron could turn around in 2024. Nvidia — The chipmaker popped 6.43% to an all-time high as Nvidia announced three new graphics chips that can power PCs or laptops and are able to power AI at home . Twilio — The enterprise communication software stock jumped 6.68% after Jeff Lawson said he would step down as CEO . Twilio has faced pressure from two activist investors pushing for changes at the company in recent weeks. — CNBC’s Michelle Fox, Alexander Harring, Yun Li, Jesse Pound and Samantha Subin contributed reporting.