Agree with Stitches. You are covered from 12:01am the day you start. Regular plan is zero dollars and is a traditional health insurance plan, not a HMO. It does not cover preventive medical, though, so all those checkups you will have to negotiate with your health care provider for the walk up rate. The company benefits people won't steer you towards this plan, they will talk up the BenefitsPlus HMO stuff. Lots of pilots love the regular plan though. It gives you good coverage and the price is right. Almost everyone who uses it comes out way ahead of paying the premium and copays for the HMO.
I don't really know much about the HSA, but that is an option as well.
I am a military guy, so I take the dental and vision for my family at around 40 a month and they pay me 50 a month to carry my own health insurance.
Here is an older pamphlet. The prices for benefitsplus have probably gone up a little since this was published.
http://www.iam141.org/contract/pdfs/...tGuide2013.pdf