diff --git a/public/js/calco2lato.js b/public/js/calco2lato.js
new file mode 100644
index 0000000..179d7b6
--- /dev/null
+++ b/public/js/calco2lato.js
@@ -0,0 +1,117 @@
+// Lightweight client that talks to your PHP proxy via fetch.
+// Returns Airport/Flight objects with helpful methods.
+
+export class Airport {
+  constructor(dto) {
+    Object.assign(this, dto);
+  }
+  get display() {
+    const code = this.iata || this.icao || '';
+    return `${code} – ${this.name}${this.city ? ' (' + this.city + ')' : ''}`;
+  }
+}
+
+export class Flight {
+  constructor(dto) {
+    Object.assign(this, dto);
+  }
+  summary() {
+    const s = [];
+    if (this.origin?.iata)  s.push(this.origin.iata);
+    if (this.destination?.iata) s.push(this.destination.iata);
+    const route = s.length ? s.join(' → ') : 'Flight';
+    const co2 = this.emissions?.co2_total ?? this.co2 ?? null;
+    return co2 != null ? `${route}: ${co2} kg CO₂e` : route;
+  }
+}
+
+export class Calco2Client {
+  /**
+   * @param {string} proxyUrl e.g. "/api-proxy.php"
+   * @param {object} [options]
+   * @param {number} [options.timeoutMs=10000]
+   */
+  constructor(proxyUrl, { timeoutMs = 10000 } = {}) {
+    this.proxyUrl = proxyUrl;
+    this.timeoutMs = timeoutMs;
+  }
+
+  async _fetchJSON(payloadOrQuery) {
+    const { method = 'GET', query = null, body = null } = payloadOrQuery;
+    const url = new URL(this.proxyUrl, window.location.origin);
+    if (query) {
+      for (const [k, v] of Object.entries(query)) {
+        if (v !== undefined && v !== null) url.searchParams.set(k, String(v));
+      }
+    }
+
+    const ctrl = new AbortController();
+    const t = setTimeout(() => ctrl.abort(), this.timeoutMs);
+
+    try {
+      const res = await fetch(url.toString(), {
+        method,
+        headers: body ? { 'Content-Type': 'application/json' } : undefined,
+        body: body ? JSON.stringify(body) : undefined,
+        credentials: 'include',
+        signal: ctrl.signal,
+      });
+      const data = await res.json().catch(() => ({}));
+      if (!res.ok) {
+        throw new Error(data?.error || `HTTP ${res.status}`);
+      }
+      return data;
+    } finally {
+      clearTimeout(t);
+    }
+  }
+
+  // ---------- Airports ----------
+
+  /**
+   * @param {string} q
+   * @param {number} [limit=20]
+   * @param {number} [offset=0]
+   * @returns {Promise<Airport[]>}
+   */
+  async searchAirports(q, limit = 20, offset = 0) {
+    const data = await this._fetchJSON({
+      method: 'GET',
+      query: { endpoint: 'airports.search', q, limit, offset }
+    });
+    const items = Array.isArray(data?.items) ? data.items : (Array.isArray(data) ? data : []);
+    return items.map(a => new Airport(a));
+  }
+
+  /** @returns {Promise<Airport>} */
+  async getAirport(code) {
+    const data = await this._fetchJSON({
+      method: 'GET',
+      query: { endpoint: 'airports.get', code }
+    });
+    return new Airport(data);
+  }
+
+  // ---------- Flights ----------
+
+  /**
+   * @param {object} params e.g. { origin: "FRA", destination: "LHR", date: "2025-09-20", pax: 1, cabin: "economy" }
+   * @returns {Promise<Flight>}
+   */
+  async estimateFlight(params) {
+    const data = await this._fetchJSON({
+      method: 'POST',
+      body: { endpoint: 'flights.estimate', params }
+    });
+    return new Flight(data);
+  }
+
+  /** @returns {Promise<Flight>} */
+  async getFlight(id) {
+    const data = await this._fetchJSON({
+      method: 'GET',
+      query: { endpoint: 'flights.get', id }
+    });
+    return new Flight(data);
+  }
+}