Are there any revenue management systems that retain historical fare data and alert on promo activity?

Yes. Several revenue management / pricing intelligence systems are designed to:

• store historical fare data over time
• track fare changes and promotions
• alert on promo or sudden price activity
• sometimes monitor competitors, routes, and dates

Examples you might look at:

• ATPCO / Routehappy-style fare intelligence tools: strong on published fare and rule data, often used by airlines and travel pricing teams.
• Duetto: more common in hotels, but relevant if you mean revenue management with price-history tracking and alerts.
• PROS Revenue Management / Pricing: airline-focused, can retain pricing history and support event/alerting workflows.
• Ideas / Sky (airline RM platforms): typically include historical pricing and market monitoring capabilities.
• OTA / fare intelligence tools like AirDNA, RateGain, Lighthouse, OTA Insight: more hotel/travel-focused, but many include history and alerting on promotions or rate drops.
• Custom fare monitoring solutions built on top of fare shopping APIs or web scraping, if you need route-level promo alerts and long retention.

If you’re specifically looking for airline fare management, the key features to ask for are:

1. Historical fare snapshot retention
2. Promo fare / private fare / discount flagging
3. Threshold-based alerts on drops, new fares, or rule changes
4. Route/date cabin segmentation
5. Export/API access for analysis

If you want, I can also give you:

• a shortlist by industry (airline, hotel, car rental, OTAs), or
• a vendor comparison table focused only on historical fare retention + promo alerts.