Lower-than-expected earnings at top tech firms spurred fresh turmoil in the U.S. stock markets on Friday after a tumultuous week that wiped out nearly all the gains made since the start of the year.

Earlier in the week, iconic manufacturers from Ford Motor Co. to Caterpillar explained how President Trump’s import tariffs are hindering their performance, and higher fuel prices in the wake of the administration's exit from the Iranian nuclear accord have dragged airline earnings down.

Some insurers, meanwhile, are seeing benefits from stronger Obamacare markets as Democrats pin their hopes to retake control of the House, the Senate or both on the success of the health law.

The following is a look at this week's numbers:

Tesla: Despite a settlement with the Securities and Exchange Commission and a defamation suit against founder Elon Musk, the electric carmaker delivered its first profitable quarter in 2018. Net income at the Palo, Alto-based company was $311 million, or $1.75 per share. Tesla was also able to lower its operating costs from the prior quarter, a key achievement after struggling to scale up production of its mass-market Model 3. Investors will be watching to see if the company can fulfill Musk’s promise to maintain profitability in subsequent quarters. Plans to launch a lower-priced version of the Model 3 could undermine that pledge. Tesla’s stock rose 5 percent Friday to $330.90 in New York trading. Full story here.

Amazon: The e-commerce giant posted net income of $2.8 billion for the most recent quarter. But a near-miss on overall sales had investors nervous about future growth, despite significant increases in the cloud service and advertising businesses. Amazon’s stock fell 7.8 percent to $1,642.81 per share. Full story here.

Alphabet: Profit at Google’s parent company rose 37 percent to $9.19 billion. The Mountain View, Calif.-based company is set to change its business model in the European Union after a $5 billion antitrust fine, but Chief Executive Officer Sundar Pichai said it's too early to tell the impact of the pending licensing shift. Google -- which is under intense pressure from the Trump administration and congressional Republicans over allegations it's biased against conservative outlets --- will likely be watching the upcoming 2018 midterm elections closely. Alphabet’s stock dropped 1.8 percent to $1,083.75. Full story here.

Boeing: After winning $13 billion in contracts in late summer, the Chicago-based aerospace giant reported a 31 percent climb in profit to $2.3 billion. Boeing raised its full-year profit outlook to as much as $15.10 a share. Deliveries in the firm’s commercial air business dipped slightly, and investors wondered whether Trump’s ongoing trade dispute with China could impact shipments of Boeing’s narrow-body 737 jet. Its top executive brushed off any concerns and said the company remains in contact with both governments. Boeing’s stock slipped 1.2 percent to $359.27. Full story here.

American Airlines: A significant jump in fuel expenses helped drag profit nearly 50 percent lower at the world’s largest carrier. Chief Executive Officer Doug Parker tried to reassure investors that the airline has “moved quickly to adapt to a higher-cost environment” by cutting flights and adding fewer routes. American’s stock inched up to $32.46. Full story here.

AT&T: The Department of Justice is trying to block a judge’s decision to allow the AT&T-Time Warner merger to advance, but in the meantime, the acquisition helped to boost profits at the telecommunications giant. Net income at AT&T increased to $4.7 billion, largely due to the transaction, which also buoyed advertising revenue to $1.5 billion. The firm is preparing to roll out its fifth-generation wireless service in 12 cities soon. AT&T slid 2.9 percent to $29.09 per share. Full story here.

Ford: A sales slowdown in China coupled with Trump’s tariffs resulted in a 37 percent drop in profits at the automaker. Ford previously announced an $11 billion restructuring effort, but the company has so far declined to provide any detail. Executives said Ford is in the “early stages” of reducing its global workforce. Its stock closed slightly lower at $8.98 per share. Full story here.

Caterpillar: The Deerfield, Ill.-based manufacturer reported a 63 percent rise in profit, but investor attention appeared to be fixed on Caterpillar’s warning that Trump’s tariffs would cost it millions. Raw-material costs were up 2 percent, Chief Financial Officer Andrew Bonfield told investors, as supply expenses rose to $9 billion. Caterpillar’s stock slipped to $115.05. Full story here.

Harley-Davidson: Amid calls from Trump to boycott the brand, profits at the Milwaukee-based motorcycle-maker rose 66 percent to $114 million. Despite the growth, U.S. sales continue to drop as Harley aims to shift more production overseas to counter Trump’s tariffs. The company has provided no details on where it plans to move its manufacturing operations. Harley’s stock tumbled 3.5 percent to $35.99. Full story here.

Centene: A stronger Obamacare market, along with more commercial customers, helped drive revenue up 36 percent to $16 billion. The St. Louis-based insurer, which operates largely in the federal insurance business, will enter four new states next year: Pennsylvania, North Carolina, South Carolina and Tennessee. Centene slid 3.17 percent to $127.25 in New York trading. Full story here.

Look ahead

More companies are scheduled to report earnings next week, including: Pfizer, Apple, GE, Honda, Aetna, Fiat Chrysler, Anthem, General Motors, Alibaba and Cigna.