Southwest Airlines’ 401(k) plan, like many institutional plans, offers three contribution buckets: traditional pre-tax, Roth, and (where the plan allows) after-tax contributions that can be converted to Roth via the in-plan mega-backdoor mechanism. For SWA pilots and employees with the income and the discipline to fill multiple buckets, the question of how to split annual contributions is one of the highest-leverage planning decisions you face every year.
There’s no single right answer. Here’s how to think about it.
The three buckets, briefly
Pre-tax (Traditional 401(k)): Contributions reduce current taxable income. Money grows tax-deferred. Withdrawals in retirement taxed as ordinary income. Subject to RMDs at age 73 (or 75 depending on birth year).
Roth 401(k): Contributions made with after-tax dollars (no current deduction). Money grows tax-free. Qualified withdrawals fully tax-free in retirement. Subject to RMDs in the 401(k); easily rolled to a Roth IRA at separation/retirement to escape RMDs entirely.
After-tax (mega-backdoor mechanism): Contributions beyond the standard $23K (2024) elective deferral limit, up to the IRS 415(c) overall limit ($69K in 2024), made with after-tax dollars. When the plan allows in-plan Roth conversions, these convert immediately to Roth treatment — effectively adding tens of thousands of additional Roth space per year. See The Backdoor Roth and Mega-Backdoor Roth, Explained.
The first $23K of your contributions can go to pre-tax, Roth, or any mix of the two — your choice. Above that, anything additional has to be after-tax, and is only useful if your plan permits the in-plan conversion.
The framework
The decision turns on one core question: is your tax rate higher today, or will it be higher in retirement?
If the answer is “higher today” → favor pre-tax. The deduction is more valuable now than later.
If the answer is “higher in retirement” → favor Roth. Pay the tax now at a lower rate; harvest tax-free growth later at a higher rate.
If the answer is “about the same” → Roth is usually still preferred because of the optionality benefits (no RMDs, easier estate planning, hedging against future tax law changes).
Why pilots are usually closer to “Roth” than they think
The standard intuition is “I’m in a high bracket now; I’ll be in a lower bracket in retirement; therefore pre-tax.” For a typical retiree, that’s usually right.
For a senior pilot at SWA, it’s often wrong. Three reasons:
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You’re going to retire on a lot. A senior captain with 20+ years of full-deferral 401(k) plus profit-sharing contributions, plus other savings, is going to retire with seven figures in pre-tax accounts. Required minimum distributions on a $3M pre-tax balance at age 73 will be approximately $113K/year — and growing. Add Social Security and any taxable account income, and you’re not in a low bracket in retirement.
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Tax rates are historically low. Federal marginal rates above 24% used to be much higher. The 2017 Tax Cuts and Jobs Act dropped them, and those provisions are scheduled to sunset (currently set for end of 2025, though Congressional action may extend them). The bet that “rates will be lower when I retire” is a bet on continued low rates over decades — not historically a great bet.
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You have a fixed retirement age. FAA Age 65 is a hard stop. You don’t have the option to “just keep working a bit longer if I need to.” Roth dollars give you flexibility — they’re not subject to RMDs, they don’t push you into IRMAA brackets, they don’t make Social Security more taxable.
For most pilots in their final 10–15 career years with a substantial pre-tax balance already accumulated, the marginal next dollar should generally go to Roth. The first $23K elective deferral split should lean Roth-heavy.
When pre-tax is still right
Several scenarios where pre-tax remains the better answer:
Early-career pilots with low pre-tax balances. The compounding asymmetry hasn’t kicked in yet. The current deduction is more valuable than the marginal future tax difference.
Single-earner households at the top of the 32% bracket where retirement spending will be significantly lower. True for some pilots, false for many.
Households with strong charitable plans. Pre-tax dollars in a traditional IRA can later be distributed as QCDs — completely tax-free. Households planning meaningful charitable giving after age 70½ should preserve some pre-tax balance specifically for QCD use.
Households where current cash flow is tight. A pre-tax contribution costs less out of pocket because it reduces current taxes. If the alternative is contributing less, pre-tax may be the right tradeoff.
The mega-backdoor Roth question
If your SWA plan allows after-tax contributions with in-plan Roth conversions (verify with HR), this is one of the most valuable wealth-building features available to high earners. The math:
- Standard elective deferral limit: $23K (2024)
- Plus profit sharing contributions from SWA
- Plus your additional after-tax contributions, up to the 415(c) limit of $69K total
For a high-earning senior pilot with the cash flow to fund it, after-tax contributions converted to Roth can add $20K–$40K of Roth balance per year — for 10+ years, that’s a quarter million or more in additional tax-free retirement assets.
The catch: requires the plan to allow it (most major-airline plans do but verify), requires you to actually have the cash flow above other obligations, and requires you to execute the in-plan conversion promptly before significant earnings accrue on the after-tax basis.
The annual decision
For most senior pilots we work with, the framework looks something like:
- First $23K of elective deferral: Roth-leaning (often 80–100% Roth) for late-career; mixed (~50/50) for mid-career.
- Profit-sharing contributions: Goes into pre-tax automatically (you don’t choose).
- After-tax contributions (if plan allows and cash flow supports): Maximize. Convert to Roth in-plan immediately.
- Plus a Backdoor Roth IRA outside the plan: $7K/year (2024 limit; spouse can do their own).
This combination, executed annually, can build $40K–$80K of new Roth space per year for a high-earning pilot — without sacrificing pre-tax planning entirely.
Every pilot’s situation is different. The right split this year may not be the right split next year. The discipline of revisiting it annually is what compounds.
If you’d like to model what your retirement balance looks like under different contribution mixes for the rest of your career, we’d be glad to do it.
General educational information for SWA pilots and employees about 401(k) contribution strategy. Plan specifics including the availability of after-tax contributions and in-plan conversions vary; verify with HR. IRS contribution limits change annually. Specific decisions require analysis of your tax situation, retirement timeline, and goals — coordinate with a tax professional.