Key Highlights

● Boeing (BA) closed at $184.39 on Monday, down from $198.07, a fall of about 6.9% that led the Dow lower.

● The FAA will not certify the 737 MAX 10 until it assesses a software issue affecting automated flight guidance.

● FAA Administrator Bryan Bedford said the agency will delay the aircraft until it is satisfied there is no issue.

● GE Aerospace supplied the software, and its shares also fell as industrials were among the S&P 500's four weakest sectors.

Boeing (NYSE:BA) plunged on Monday, September 28, after the Federal Aviation Administration delayed certification of the 737 MAX 10 over a software issue. The stock closed at $184.39, down from $198.07 on Friday, a fall of about 6.9%. The Dow Jones Industrial Average fell 347.11 points to 51,481.51, and Boeing was its biggest drag. The Dow is a price-weighted index of 30 large US companies. Because it is weighted by share price rather than market value, a big dollar move in one stock can swing the whole index.

What the FAA Flagged

The FAA said it will not certify the 737 MAX 10 until it assesses a newly flagged software issue. According to the FAA, automated flight guidance can be unavailable in some landing and go-around scenarios. A go-around is when pilots abort a landing and climb away to try again. The FAA said the software "can increase pilot workload when doing a go-around."

The software was supplied by GE Aerospace (NYSE:GE), according to reports, and GE's shares also fell on the day.

FAA Administrator Bryan Bedford said: "We will be delaying the 10 until we're satisfied that we don't have an issue here." A Boeing spokesperson said: "We continue to follow the lead of the FAA as we work through the certification process."

Why the MAX 10 Matters

The 737 MAX 10 is the largest version of Boeing's best-selling narrow-body jet family, designed to compete with Airbus's A321neo. Airlines have ordered it in large numbers, and certification is needed before deliveries can begin. Every delay pushes back when Boeing can hand over those planes and collect payment, which affects its cash flow.

That is why investors reacted so sharply. The stock lost $13.68 a share, a fall of about 6.9%.

A Rough Day Made Worse

Boeing's slide came on a weak day for the whole market. Industrials were among the four S&P 500 sectors that fell the most, per exchange data. The 10-year Treasury Yield hit its highest level since 2007, oil climbed after President Trump rejected Iran's Hormuz proposal, and higher jet-fuel costs are a concern for aviation broadly.

Boeing's drop led the Dow lower. Nvidia (NASDAQ:NVDA)'s gain of less than $4 a share was nowhere near enough to offset it.

The FAA Timeline Is Boeing's Next Catalyst

The key question is how quickly the FAA completes its review. Any update from the regulator or Boeing on a software fix or a new timeline could move the stock sharply, and investors will also watch for comments from airlines that have ordered the MAX 10.

GE Aerospace is worth watching too, given its role as the software supplier. On the macro side, JOLTS and consumer confidence arrive Tuesday, PCE Inflation Wednesday, ISM Manufacturing Thursday and the September jobs report Friday, and ISM manufacturing offers a broad read on the industrial economy that Boeing sits at the centre of.