here is the problem that we face.
We have LGA-YYZ flight however my SO has a EU passport and american(american naturalization certificate) but not US passport. Since the trip is this Sunday would she be able to board and enter Canada with her EU Passport(not eligible for visa waiver for Canada) and the naturalization certificate which proves that she is an American(albeit with no US passport). Afaik americans do not need visas to enter Canada.

Cannot find a single proof that this is possible but I could be wrong.

If you travel before the 15th, EU citizens don't need an ETA to fly into Canada. According to: http://www.cic.gc.ca/english/visit/visas.asp

Why don't you think your SO is eligible for a visa waiver? Is there something on her record that would prevent her from being admissible to Canada?

Nationals of European Union countries are generally eligible to visit Canada without a tourist visa.

The new Canadian ETA program (similar to US ESTA) is not a visa. This may be an issue of semantics, but the US did the same thing when the ESTA was introduced. ESTA and ETA are required by visa waiver travellers into the USA and Canada respectively. Canadians and Americans are "visa exempt" when visiting each others' countries.

The ETA program was to have become mandatory with effect from 15-March (before your entry date) so it would not apply to your SO on this coming Sunday. The Canadian government announced a few days ago that the start date has been pushed out by six months.

Your SO can travel to Canada on an EU passport without taking any other measures, prior to the restart ETA program in the fall of 2016.
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13F

Guys I do not think it will work. She is from Bulgaria which is in the EU but not on the EU eligible countries to enter Canada. The thing then is can she enter with the said EU passport and the US Naturalization Certificate proving that she is also an american?
the site says:
Visa-exempt foreign nationals are expected to have an Electronic Travel Authorization (eTA) to fly to or transit through Canada, starting March 15, 2016. Exceptions include U.S. citizens, and travellers with a valid Canadian visa. Canadian citizens, including dual citizens, and Canadian permanent residents are not eligible to apply for an eTA.

Yes but would AA accept a citizen naturalization certificate and an EU passport that does NOT grand entry by itself? Thats the big question

Presuming that she is located in Washington along with you, she can obtain an expedited US Passport at the Passport Agency in downtown Washington (see the link). She will need proof of travel and all of her completed forms (all available online), as well as photos which meet the exact specifications (just use the photo place next to the Passport Agency and don't create delays or problems).

https://travel.state.gov/content/pas...ashington.html

She faces several issues if she does not.

First, if she is a USN, AA will not accept anything other than a US Passport as proof of US citizenship. If that is an issue, AA may not permit her to board and the entire issue of what public officials do is never reached.

Second, the US requires that its Nationals travel on a US Passport. As a USN, she may not be denied entry to the US, but she may theoretically be fined for traveling on another nation's travel documents. (not very likely) and the process of clearing without a Passport may be a hassle.

All of this avoided if she simply obtains the US Passport which she ought to obtain anyway.

http://www.cbsa.gc.ca/travel-voyage/td-dv-eng.html#_s2a

According to this page:
Identification requirements for U. S. citizens and permanent residents
If you are a U.S. citizen, ensure you carry proof of citizenship such as a passport, birth certificate, a certificate of citizenship or naturalization, or a Certificate of Indian Status along with photo identification. If you are a U.S. permanent resident, ensure you carry proof of your status such as a U.S. Permanent Resident Card.

Whether you�re entering by air, land or water, we recommend you carry a valid passport for all travel abroad, including visits to Canada from the U.S. A passport may be required by your airline or alternative transportation authority, as it is the only universally-accepted identification document.
==more==
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13F

Often1 actually you are incorrect. Here are the reqs taken out of TIMATIC(what AA checks then checking folks in):
Canada - Destination Passport

Passport required.

Travel without passport is possible for:

Nationals of the USA with a recommended proof of citizenship such as a:
- US birth certificate; or
- US certificate of citizenship; or
- US certificate of naturalization.

Document validity rules:

Passports and other documents accepted for entry must be valid for the period of intended stay.

Warning: if departing from the USA (regardless of any destination passport exemptions), a valid passport and/or accepted departure document is required by the US immigration authorities.

Additional information:

Holders of proof of citizenship issued by USA not holding a valid passport; will be granted entry upon arrival only after examination by a Canadian Border Services Officer if having satisfied the officer about their citizenship.

So there we have it. It will be 100% fine as this is what the above says. She will have to go through a secondary in YYZ but we will be totally fine with that!

Have a smooth flight and a pleasant stay in YYZ.
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13F

I am indeed correct. You have only 50% of the equation. I never remotely suggested that your SO won't be admitted to Canada. Only that she may (likely will) be denied boarding by AA because CBP requires that departing air pax have a Passport and that USN's travel on their US Passport.

TIMATIC is IATA's website database and, while it is true that AA generally relies on it, all of the LGA agents (frankly all agents at US departure points) are well aware that CBP rules require a Passport for air departures from the US (for whatever reason, no such requirement for land crossings). I excerpted the language below and also provided a full link. Your SO is, of course free to attempt whatever she wants, but because others read this board, its important for them to know that you posted 1/2 of the rules and if it works for your SO that's great, but doesn't mean that it will in general.

Also, I noticed that while you show DC as home base, your SO is departing LGA. Presuming that she is NYC-based, there is also a Passport Agency in NYC which can handle expedited Passport issuance.

Will a bored AA agent boarding a routine transborder flight care about all of this? Maybe. If he does, your SO won't be traveling and will wish that she had paid a simple visit to the Passport Agency. If the agent doesn't, she'll have her visit to Canada with perhaps a secondary on either end. It's all about risk tolerance.

Document Requirements for Air Travel
All U.S. citizens ... departing from or entering the United States from within the Western Hemisphere at air ports of entry are required to present a valid passport, NEXUS card....

http://www.cbp.gov/travel/us-citizen...ocs-air-travel

Often1
it actually appears that you are indeed incorrect. Had a friend talk to an agent in LGA that confirmed that Foreign passport + anything that shows that the person is an american(green card, asulym docs, naturalization cert) will be issued BP. So case closed. She will be able to get BP and get on the plane will just have to go through secondary in YYZ which will be totally fine for us