The S&P/ASX 200 Index (ASX: XJO) is starting the week in the red. In afternoon trade, the benchmark index is down 0.55% to 9,146.2 points.
Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

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Brainchip Holdings Ltd (ASX: BRN)
The Brainchip share price is down 9.5% to 14 cents. This struggling semiconductor company's shares have come under pressure again since the release of its full-year results last week. It was another disappointing release, with Brainchip reporting revenue of US$1.9 million and a massive operating loss of US$21.7 million for the 12 months. Investors appear to be doubting whether Brainchip will ever gain any meaningful commercial traction given how it is competing with companies that have R&D budgets that dwarf its own.
Fortescue Ltd (ASX: FMG)
The Fortescue share price is down 4% to $20.24. This has been driven by the iron ore giant's shares going ex-dividend this morning for its latest payout. Last month, Fortescue released its half-year results and reported a 23% increase in net profit after tax to US$1.9 billion. This allowed the Fortescue board to increase its fully franked interim dividend by 24% to 62 Australian cents per share. Eligible shareholders can now look forward to receiving this dividend later this month on 30 March.
Qantas Airways Ltd (ASX: QAN)
The Qantas share price is down 6% to $9.36. This appears to have been driven by war in the Middle East after the US struck Iran. And with Iran retaliating against its neighbours, this could impact travel demand in the near term. In addition, it is expected to cause oil prices to spike. And given how fuel is an airline's biggest operating cost, this could have a negative impact on its second-half earnings. A number of other ASX travel stocks are trading lower today in response to the news.
Westpac Banking Corp (ASX: WBC)
The Westpac share price is down 3% to $41.22. This is despite there being no news out of Australia's oldest bank. However, it is worth noting that all of the big four banks are trading lower today. This could have been driven by profit-taking from some investors after strong gains were recorded in the sector in February. This has seen the S&P/ASX 200 Financials index tumble by 2.7% on Monday afternoon.