No, as of January 2017 the iPad 1 is no longer supported by ForeFlight. Since late 2014, all apps for the iPad 1 have been "fixed in time” because Apple stopped allowing developers to release app updates for them. Continuing support for the iPad 1 would prevent our server infrastructure from being updated to be more secure and to offer more capability with each new app update.
Any newer iPad will not only perform much better than the iPad 1, but will give you access to all of the features and improvements we have introduced in ForeFlight Mobile since January 2014. You can view recommended iPads in the iPad Buying Guide.