There's no doubt that money can be made by owning shares of unprofitable businesses. For example, biotech and mining exploration companies often lose money for years before finding success with a new treatment or mineral discovery. But while the successes are well known, investors should not ignore the very many unprofitable companies that simply burn through all their cash and collapse.

So should Lilium (NASDAQ:LILM) shareholders be worried about its cash burn? For the purposes of this article, cash burn is the annual rate at which an unprofitable company spends cash to fund its growth; its negative free cash flow. Let's start with an examination of the business' cash, relative to its cash burn.

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How Long Is Lilium's Cash Runway?

A company's cash runway is calculated by dividing its cash hoard by its cash burn. As at December 2023, Lilium had cash of €195m and no debt. Importantly, its cash burn was €261m over the trailing twelve months. So it had a cash runway of approximately 9 months from December 2023. To be frank, this kind of short runway puts us on edge, as it indicates the company must reduce its cash burn significantly, or else raise cash imminently. You can see how its cash balance has changed over time in the image below.

How Is Lilium's Cash Burn Changing Over Time?

Lilium didn't record any revenue over the last year, indicating that it's an early stage company still developing its business. So while we can't look to sales to understand growth, we can look at how the cash burn is changing to understand how expenditure is trending over time. It's possible that the 2.2% reduction in cash burn over the last year is evidence of management tightening their belts as cash reserves deplete. While the past is always worth studying, it is the future that matters most of all. So you might want to take a peek at how much the company is expected to grow in the next few years.

Can Lilium Raise More Cash Easily?

Even though it has reduced its cash burn recently, shareholders should still consider how easy it would be for Lilium to raise more cash in the future. Issuing new shares, or taking on debt, are the most common ways for a listed company to raise more money for its business. Many companies end up issuing new shares to fund future growth. By comparing a company's annual cash burn to its total market capitalisation, we can estimate roughly how many shares it would have to issue in order to run the company for another year (at the same burn rate).