I'll say this straight out: I'm skeptical of Boeing's (NYSE: BA) valuation. At $66 and change, Boeing shares cost 13 times earnings...but 77 times free cash flow, and are trading at about a 0.75 price-to-sales ratio, fairly close to the one times sales ratio that's been the historical norm for defense and aerospace companies. (In fact, Boeing's a bit ahead of defense space rivals Textron (NYSE: TXT), Northrop Grumman (NYSE: NOC), and Lockheed Martin (NYSE: LMT), for example, each of which sells for only about 0.5 times sales today.)

But if Boeing keeps going as it's been doing for much longer, it might convert even this skeptic.

Boeing, going, gone!
Fresh from recording its biggest airplane order ever, Boeing returned to market today and announced it's just recorded an even bigger order. (It's "biggest-er" order ever?) Last week's order was for long-haul 777s, sold to Dubai's Emirates Airlines. At $18 billion, with an additional $8 billion in "optioned" planes, that order was pretty big news already. But Boeing just topped it with the deal announced this morning.

In a massive 230-plane sale, Boeing proposes to outfit Indonesia's largest private airline, Lion Air, with a shiny new fleet of 737 MAX airplanes and extended-range 737s as well. The initial purchase, valued at list prices, comes to $21.7 billion. And later on, Lion Air has the option to expand this order by an additional 150 planes -- taking Boeing's total haul past $35 billion.

To lend some perspective, this win is even bigger than the 200-plane deal that Boeing inked with American Airlines parent AMR back in July. That was the deal that sparked the upgrade from 737 to 737 MAX in the first place, when Boeing shelved plans to develop a new short-haul airplane, and instead upgraded the 737 with new engines from General Electric's (NYSE: GE) CFM joint venture. So over the course of just four short months, Boeing has placed three "biggest ever" orders in quick succession.

Foolish takeaway
So far this year, Boeing shares have lagged the performance of the Dow Jones Industrial Average (INDEX: ^DJI) slightly. But over at Forbes, analysts have been hypothesizing that last week's sale might help add $24 or so to Boeing's stock price, and push the stock to $91. Now, Boeing's done itself one better -- and made today a terrific day to be a Boeing shareholder.

Ah, but will it be enough to push Boeing stock past the $100 mark? Add this stock to your Fool Watchlist, and find out.

Fool contributor Rich Smith does not own (or short) shares of any company named above. The Motley Fool owns shares of Lockheed Martin, Northrop Grumman, and Textron. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.