Aviationstack ◆
Aviationstack is a scalable REST API for real-time flight tracking, historical flight data, airport info, and global aviation data.

Hapio (Developer Tools): Hapio is a headless booking & scheduling API that lets you build custom booking features into any app or website. Pricing: from from €0/mo. (data verified July 2026)
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Hapio is a headless booking and scheduling API designed for developers and businesses that need to add custom booking functionality to their applications. Instead of a pre-built calendar widget, Hapio provides a RESTful API and webhooks that give you full control over the user interface and booking logic — making it ideal for SaaS platforms, marketplaces, healthcare systems, and any industry that requires dynamic scheduling.
Hapio is built for product teams, software developers, and technology companies who need a scalable booking backend without the constraints of a white-label or template-based solution. It works with any modern tech stack (React, Vue, .NET, PHP, etc.) and is especially suited for use cases in healthcare, recruitment, education, fitness, travel, and e-commerce. It is not for non-technical users who want a plug-and-play booking widget — Hapio requires development work to integrate.
Hapio handles resources, services, time zones, appointments, availability logic, conditions, and more — all through a serverless architecture that scales automatically. Developers get a well-documented API, flexible API token permissions, a developer portal with logs, and the freedom to design every step of the booking flow. The platform is white-label by nature (no Hapio branding is forced), making it ideal for embedding scheduling into your own product.
Editorial score from our review methodology — not user ratings.
Hapio pricing: from €0/mo.
€0/month per project — Up to 1,000 requests/month, rate limit 100 req/min. No credit card required. Ideal for development and testing.
€29/month per project — 10,000 included requests/month, rate limit 250 req/min, €0.0029 per additional request. Best for small projects.
€249/month per project — 100,000 included requests/month, rate limit 500 req/min, €0.0029 per additional request. For small to medium projects.
€599/month per project — 250,000 included requests/month, rate limit 1,000 req/min, €0.0029 per additional request. For large projects.
From €1,500/month — Unlimited requests, unlimited team members, custom rate limits, Premier Support. Contact for a quote.
All plans are pay-as-you-go (except the free Build plan). Start with the free plan — no credit card needed.
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