sftvlr is correct - but I'll add a clarification.

When checking bags through to a final destination on multiple carriers, the only thing that matters is that both airlines have an interline baggage agreement. The ability to pull up an e-ticket reservation has no material impact on baggage transfers - it only matters for interline boarding pass issuance (another story entirely with UA).

Normally, low cost carriers (like Norwegian) do not have interline bag agreements with anybody, so you need to factor in the retrieval of baggage at your transit point into your schedule. This applies to all major LCCs, including Southwest, JetBlue, Ryanair and EasyJet - a major downside to LCCs if you are trying to combine them with an intl ticket and are checking bags.

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