Rolls-Royce (LSE:RR.) shares are down 3.5% this month, one of the most significant dips for the aerospace engineering firm in over a year of gains. If the price closes down this month it’ll be the first time in six months it closed lower. But the decline isn’t particularly surprising. The share price recently touched £4.35, the highest it’s been in over 10 years. Having risen six-fold in the past 18 months, it’s hardly surprising that the stock is running out of steam. And yet there are many reasons to believe it could keep going up. With Rolls-Royce still reporting high revenue there could be room for further gains. Throughout 2023, demand for its engines increased along with an increase in air travel. For now, there’s no immediate reason this trend will stop. It’s also seen increased demand due to defence spending related to the conflict in Ukraine. This is also ongoing. Based on estimated future cash flows, the £4 price may be below fair value – by over 50%. Using a discounted cash flow model, analysts estimate a price of around £8.90 to be more fair. Even with the rapid earnings growth in 2023, the trailing price-to-earnings (P/E) ratio of...