In this section, you'll learn about your options when you're a few miles short, or want to combine miles from multiple accounts or programs, including Aeroplan's ground-breaking new Family Sharing program.
Buying Miles
If you're a little short for an award, Aeroplan allows you to buy up to 50% of the miles needed for that redemption, at a cost of 3 cents CAD per mile. That's pretty expensive compared to the regular value of miles, so I would consider it a last option; you're much better off transferring miles if at all possible.
Other programs like Alaska allow you to buy miles up to the full value of an award, but put a limit on the total number of miles you can buy in a year. The dirty little secret here is that Alaska Miles are priced relatively cheap, compared to what you can use them for; for example, you'll pay $1,478.13 USD (~$1,900 CAD) to buy the 50,000 miles you'll need for a one-way, business-class Cathay Pacific flight from North America to Asia, that would otherwise cost over $6,000.
Alaska also offers sales on purchased miles from time to time, in which you might receive 10-30% bonus miles on top of your purchase.
Before you get too excited, the catch with this trick is that it takes a few days for Alaska's (non-refundable) miles to show up in your account, and if someone else snaps up that award in the meantime, you'll have to use the miles for a different flight. The best time to use this trick is when your search for Cathay award flights shows a flight with several seats available in the specific flight and cabin you want; I've seen as many as 7 business award seats on one Cathay flight.
Transferring Miles Between Accounts
Several mileage programs allow miles to be transferred from one account to another, but this works very differently from one airline program to the next.
For example, Alaska miles can be transferred from one account to another, in blocks of 1,000 at a time, for 1 cent per mile (USD).
Aeroplan's new Family Sharing program
While Aeroplan previously placed a stiff surcharge on any miles transfer, their recent merger with Air Canada included the announcement of their Family Sharing program. This gets pretty detailed, but the short version is that you can now join a Family Sharing group with up to 7 other people - related or not - and pool your miles for awards you might not otherwise afford individually.
Two big details here - watch these carefully!
First, to prevent people abusing the rules, once you join a Sharing group, you've got to stay in it for 3 months, and if you leave one Sharing group, you won't be allowed to join another for 6 more months.
Second, when redeeming awards from a Sharing group, miles are deducted from each member's account based on whatever percentage of the group total they owned at the time.
For example, let's say Mom, Dad and Kid decide to buy Kid a vacation trip for her birthday, and redeem for a flight that costs 100,000 miles. At the time of purchase:
Mom's account had 200,000 miles
Dad's account had 100,000 miles
Kid's account had 50,000 miles
Together, the group has 350,000 miles.
So, Aeroplan calculates percentages and sees that of the 350,000 total, Mom has (200 / 350 = ~57%); Dad has (100 / 350 = ~29%); and Kid owns (50 / 350 = ~14%).
When taking miles from each account to purchase the award flight, Aeroplan will use these percentages to deduct ~57,000 miles from Mom, ~29,000 miles from Dad, and ~14,000 miles from Kid.
Make sense?
Obviously, you'll need to think carefully about who you get into a Sharing group with. There is a feature where the group "host" can choose which members are allowed to make award redemptions, though each user always has the ability to leave at any time.
Transferring Miles From Hotel Loyalty Programs
Given the sheer number of hotel programs out there, and the wide range of values each program gives to one point, I'll keep this general. It's possible to transfer hotel loyalty points into a variety of airline programs, but it's usually not a very good deal.
For example, 25,000 IHG points transfer to 5,000 Aeroplan miles. I would value those IHG points at $150-200, and those Aeroplan miles at about $100, but since many people have a few thousand points in each of several hotel programs, it might work well for some users who have some of each, but not quite enough of either.
The one standout here is Marriott (formerly SPG) points, which I value highly simply because they transfer to so many different airline programs, and give a 25% bonus when transferred in chunks of 60,000 at a time. So, for example, 30,000 Marriott points would transfer to 10,000 Aeroplan or Alaska miles, but 60,000 Marriott points would transfer to 20,000 Aeroplan or Alaska, plus a "bulk-buy" bonus of another 5,000 airline miles.
Important: Because every hotel program's miles are of a different value, I strongly suggest doing a bit of math before you convert. The right question to ask is, "am I better off using these hotel points for free hotel rooms?" Personally, I tend to get better value out of the airline miles, but I just don't care that much about a crazy-amazing hotel.
For me, hotel points are most valuable when used for a high-demand booking like Times Square on New Year's Eve, or London during peak tourist season; the points cost of a room might be 40,000 any night of the year, while the cash price for the same room might go from $150 on a low-demand weeknight, to $400 when there's a convention or major sporting event in town.
The point is, knowing the value of your miles, and planning strategically, can easily turn a nice little savings into a big win!