As a dispatcher, I pick alternates all the time, and like most things associated with aviation, there are numerous variables involved.
First, and a minor point, was the captains use of the term "groundstop". ATC might have stopped taking arrivals, but "groundstop" is what occurs to the flights destined to BWI
from other points, i.e. ATL
was stuck at ATL
Back to alternate selection, etc. Most simply stated, destination alternates need to be specified when the destination is/is forecast to have less than a 2,000 cloud ceiling or less than 3 miles visibility. (I'm leaving thunderstorms out of the equation for the moment.) If I was releasing a XYZ-DCA
flight with, say, a 1,800 foot ceiling at DCA
, I'd specify IAD
as the alternate, since it doesn't require much fuel to get there. It's almost a certainty that the flight will get into DCA
as planned, and in this case, IAD
is what we refer to as a "paper" alternate. "Paper" alternates are commonly airports that an airline doesn't fly into normally, i.e. "off-line" alternates.
Now, when it comes to thunderstorms, or for that matter, fog, any of which could drastically increase the chances of not being able to land, alternate selection and use becomes less "what-if" and more "when". Off-line diversions are usually not preferable, as there is nobody at the diversion airport working for your airline, and you're then at the mercies of another airline (who may be dealing with their own diversions) or a fixed-base operator (FBO). On-line diversions are preferable, since their avoid some of these problems, and you also then have company personnel in place to handle passengers should the flight have to cancel.
In the case of your Frontier flight, they also serve one of the NYC airports (LGA
, I think) but quite often, the weather that 's causing the problems at DCA
is also entailing problems getting into NYC, hence the use of IND
. The dispatcher would have had the option of changing the alternate from IND
, or Richmond VA (RIC
), assuming the weather permitted, so as to use some of the fuel for getting to IND
for use in holding, since IAD
are closer, but that increases the risk of diverting off-line, perhaps one they didn't want to take. Another factor, for some airlines, not necessarily Frontier, is that other airports like CVG
, might already have other divereted flights, and not be able to be handled.
There are still some other factors, undiscussed, but those are the major ones applicable to your situation.
Hope this helps...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.